VBA logic when using macros from personal.xls - vba

Question

I run a spreadsheet report that holds about 50 columns of data for anywhere from 1 to 5000 rows. I'm only interested in 4 columns, but they are never in the same location as these reports are set-up a bit differently for each client. I then take those 4 columns and paste into a new workbook that I can import into another program.
I have three macros created that accomplish this task flawlessy if ran from the local file. When I load them into the personal.xls for use on various files I have issues. Specifically workbook/worksheet referencing issues.
Parts of the macro run to the sheet I intend from them to result on, while other parts act on the personal.xls file itself. This confuses me because I don't have any lines that use commands such as 'thisworkbook' or 'activeworksheet'.
For example:
- The first line is coded to rename Sheet1. The macro renames Sheet1 in personal.xls.
- The next line is the first of four Find commands that locate where the columns i'm interested are located and then move them. This macro runs perfectly on the sheet I intend.
I think my best course is to begin each macro by naming the active workbook and then breaking out each command to the workbook level instead of starting with Worksheets, Range, etc.
Can anyone help me understand what VBA is thinking when performing macros from personal.xls and how to best avoid the macros being run on that sheet itself?

Answer 1

There are two approaches you can take. I use one or both in my code - it's not a one or the other situations.
Declare Variables
Start by defining each sheet that you want to work on in a variable. I generally stay at the sheet level, but that's just a personal choice. If you'd rather be at the workbook level, that's OK too. A procedure might looks like:
Dim shSource as Worksheet
Dim shDest as Worksheet
Set shSource = Workbooks("SomeBook").Worksheets(1)
Set shDest = ActiveWorkbook.Worksheets("Summary")
then whenever I reference a Range or Cells or anything else on a sheet, I preface it with that sheet object variable. Even if I need to get to the workbook, I start with the sheet. If I needed to, for instance, close the Source workbook from the above example, I would use
shSource.Parent.Close False
I set up the sheet variables I need and then everything I do is in terms of those variables.
Edit
If you're opening or creating workbooks, then variables is definitely the way to go. For example, if you're opening a workbook, you could use one of these two examples
Dim wb As Workbook
Set wb = Workbooks.Open(C:\...)
Dim ws As Worksheet
Set ws = Workbooks.Open("C:\...).Worksheets(1)
or creating new, one of these two examples:
Dim wb As Workbook
Set wb = Workbooks.Add
Dim ws as Worksheet
Set ws = Workbooks.Add.Worksheets(1)
With Blocks
When I'm only trying to get at something one time, it seems like a waste to set up a bunch of variables. In those cases, I use a With Block so I can still have fully qualified references, but without a bunch of clutter in my code.
With Workbook("MyBook")
With .Worksheets("First_Sheet")
.Range("A1").Value = "stuff"
End With
With .Worksheets("Second_Sheet")
.Range("G10").Formula = "=A1"
End With
End With
I probably prefer the variable method, but I use them both.
Edit 2: Implicit Referencing
You should always explicitly reference your workbooks and worksheets, but it's still instructional to know how Excel will behave if you don't. A line of code that starts like Range("A1").Value = ... is called an unqualified reference. You're referencing a range, but you're not saying which sheet its on or which workbook that sheet is in. Excel handles unqualified references differently depending on where your code is.
In a Sheet's Class Module (like where you use sheet events like SelectionChange), unqualified references refer to the sheet represented by that module. If you're in the Sheet1 module working in the Change event and you code x = Range("G1").Value then the G1 you are referring to is on Sheet1. In this case, you should be using the Me keyword rather than relying on Excel.
In any other module (like a Standard Module), unqualified references refer to the ActiveSheet. The same x = Range("G1").Value code in a Standard Module refers to G1 on whichever sheet has the focus.
Excel's treatment of unqualified references is very reliable. You could easily create robust code by relying on Excel to resolve the qualified references. But you shouldn't. Your code will be more readable and easier to debug if you qualify every reference. I qualify every reference. And that's not one of those things I "always" do except when I'm lazy - I really do it 100% of the time.