Nested For...Next loops to copy and paste several times - vba

Question

I want to copy the cells "A2:A" & patientprofiles + 1 and paste them in the first unused row in column D (i.e., there should be no blank cells between what's already in column D and what I want to paste there, but I also don't want to paste over what's already there). I then want to repeat this process a user-defined number of times (this variable will be called g1_observations). I then want to copy the cells "A" & patientprofiles + 2 & ":A" & 2 * patientprofiles + 1 to the new last used row in column D (i.e., taking into account that I've just pasted patientprofiles number of cells g1_observations number of times at the bottom of column D. I want to continue repeating this process a user-defined number of times (this number of times is defined by the variable numberofgrids).
For example: imagine that the user has defined that there will be three grids. Grid 1 will have 2 observations, Grid 2 will have 3 observations, and Grid 3 will have 4 observations. Also imagine that patientprofiles has been set to 40.
If this is the case, there will already be values in cells D1:D121, so I want to begin pasting in D122. I want to paste the cells A2:A41 (40 cells because patientprofiles = 40) to cells D122:D161; I want to paste the cells A42:A81 to cells D162:D201 and again to D:202:D241; and I want to paste cells A82:A121 to cells D242:D281, again to cells D282:D321, and again to cells D322:D361. I'm pasting each "grid" one less time than the number of observations for that grid, because the first group of observations for all grids is what's contained in cells D2:D121. End example
I'm pretty sure I need to use a nested For...Next loop in order to do this, but I'm having trouble with both the inner and outer loop. I think the outer loop should go something like this:
Dim i as long
For i = 0 to numberofgrids - 1
[insert inner loop here]
Next
As far as the inner loop goes, I'm not really sure what I'm doing because it keeps pasting over itself when I am pasting from two grids. The current code I have uses repeated For...Next loops and doesn't work:
Dim myLastRow as Integer
myLastRow = Worksheets("Work").UsedRange.Rows.Count
Dim j as Long
For j = 1 To g1_observations - 1
If j = 1 Then
Range(Cells(2, 1), Cells((patientprofiles + 1), 1)).Copy _
Destination:=Worksheets("Work").Cells(j * myLastRow + 1, 4)
ElseIf j > 1 Then
Range(Cells(2, 1), Cells((patientprofiles + 1), 1)).Copy _
Destination:=Worksheets("Work").Cells((j + 1) * (myLastRow / 2) + 1, 4)
Else: Range("A1").Select
End If
Next
For j = 1 To g2_observations - 1
If j = 1 Then
Range(Cells(patientprofiles + 2, 1), Cells((2 * patientprofiles + 1), 1)).Copy _
Destination:=Worksheets("Work").Cells(j * myLastRow + 1, 4)
ElseIf b > 1 Then
Range(Cells(patientprofiles + 2, 1), Cells((2 * patientprofiles + 1), 1)).Copy _
Destination:=Worksheets("Work").Cells((b + 1) * (myLastRow / 2) + 1, 4)
Else: Range("A1").Select
End If
Next
It pastes over itself, and sometimes it skips lines. I can't really figure out how to reconcile myLastRow with a loop.
I think the inner loop should probably start off something like this:
Dim j as Long
For j = 0 to gj_observations - 1
Range(Cells(j * XXX + 2, 1), Cells((j + 1) * patientprofiles + 1).Copy _
Destination:=Worksheets("Work").Cells(myLastRow * j + 1) , 4
but I'm having difficulty because the variables are called g1_observations, g2_observations, g3_observations, etc., all the way up to g10_observations, and obviously gj_observations won't work. I want to loop on the number between "g" and "_", but I don't know how to get VBA to read variables that way, or if that's possible at all.
Can anyone help me out here? My mind is spinning from trying to understand the concept of loops, especially with different variables at each level.
Also, side question, how do you tell VBA to do nothing in an If statement? I currently have it selecting A1 by writing Else: Range("A1").Select, but I'm sure there's a better way of doing it.

Answer 1

When you're writing macros, it's a better practice to work with ranges and avoid manipulating cells one at a time in a loop. Your macro will run much faster and the code will be clearer.
If you want to create a set of variables that you can access by number, you would use something called an array. This is a pretty fundamental concept that exists in almost every programming language, so I'll refer you to MSDN or your favorite VBA language reference guide for more details.
Dim ws As Worksheet
Dim lr As Long ' Last Row
Dim szpp As Long ' Size (rows) patient profiles
Dim szgobsrv(2) As Long ' Size (rows) observation groups
Dim i As Long
Dim j As Long
Dim SourceCells As Range
Dim TargetCell As Range
Set ws = Sheets("Work")
szpp = 40
szgobsrv(0) = 1
szgobsrv(1) = 2
szgobsrv(2) = 3
For i = 0 To UBound(szgobsrv)
lr = ws.UsedRange.Row + ws.UsedRange.Rows.Count - 1
' copy the patient profile cells multiple times depending on group size
For j = 0 To szgobsrv(i) - 1
Set SourceCells = ws.[A2].Offset(i * szpp).Resize(szpp)
Set TargetCell = ws.[D1].Offset(lr + j * szpp)
SourceCells.Copy TargetCell
Next
Next
Note the usage of the Resize and Offset methods. These are helpful Range methods that can change the size and position of a range by a fixed amount.

Answer 2

The main problem you are having with values being over written is that youre not using Offset.
Another important thing to remember about nested loops is that the nested loop runs i times per loop of the upper level loop. I am thinking that nested loops here might not be good for you. You could probably just make them all independent loops?
If you want to loop to the number contained within the variable you might want to set that variable equal to a number.
example:
g2_observations =2
For j = 1 To g2_observations - 1
Aside from this I am actuall yhaving difficulty understanding what you need, but hopefully this helps?
numberofgrids = input
i = 1 to numberofgrids
gridCount = gridCount + 1
'Loop Stuff
Case Select gridCount
Case is = 1
'logic
Case is = 2
'logic
Etc etc
End Select
If numberofgrids = gridCount Then
Exit For
End If
Next i