VBA code to add days from one column to another - vba

Question

I'm having the following columns in Excel: Document Date (all cells have values) & Initial Disposition Date (there're blanks within the column).
Each Document Date cell corresponds to an Initial Disposition Date cell.
For any blank Initial Disposition Date cells, I'd like to set them to be 7 days from the corresponding Document Date. (Strictly blank cells)
Ex: Document Date = 10/01/2018. Desired Initial Disposition Date = 10/08/2018.
Is there a code to execute such action? (I have approximately 55,000 rows and 51 columns by the way).
Thank you very much! Any suggestions or ideas are highly appreciated!

Answer 1

Looping through a range is a little quicker in this case. I am assuming your data is on Sheet1, your Document Date is on Column A and your Initial Deposition is on Column B.
Last, you need to determine if you want that 7 days to be inclusive of weekends or not. I left you a solution for both. You will need to remove one of the action statements (in middle of loop)
Option Explicit
Sub BetterCallSaul()
Dim ws As Worksheet: Set ws = ThisWorkbook.Sheets("Sheet1")
Dim LRow As Long, iRange As Range, iCell As Range
LRow = ws.Range("A" & ws.Rows.Count).End(xlUp).Row
Set iRange = ws.Range("B2:B" & LRow)
Application.ScreenUpdating = False
For Each iCell In iRange
If iCell = "" Then
iCell = iCell.Offset(, -1) + 7 'Includes Weekends
iCell = WorksheetFunction.WorkDay(iCell.Offset(, -1), 7) 'Excludes Weekends
End If
Next iCell
Application.ScreenUpdating = True
End Sub

Answer 2

If your Document Date is on Column A and you Initial Disposition Date in Column B, then the following would achieve your desired results:
Sub foo()
Dim ws As Worksheet: Set ws = Sheets("Sheet1")
'declare and set the worksheet you are working with, amend as required
Lastrow = ws.Cells(ws.Rows.Count, "A").End(xlUp).Row
'get the last row with data on Column A
For i = 2 To Lastrow
'loop from row 2 to the last row with data
If ws.Cells(i, "B").Value = "" Then
'if there is no value in Column B then
ws.Cells(i, "B").Value = ws.Cells(i, "A").Value + 7
'add seven days to the date from Column A
End If
Next i
End Sub

Answer 3

A formula on all blanks would avoid the delays looping through the worksheet column(s).
Sub ddPlus7()
Dim dd As Long, didd As Long
With Worksheets("sheet1")
'no error control on the next two lines so those header labels better be there
dd = Application.Match("Document Date", .Rows(1), 0)
didd = Application.Match("Desired Initial Disposition Date", .Rows(1), 0)
On Error Resume Next
With Intersect(.Columns(dd).SpecialCells(xlCellTypeConstants, xlNumbers).EntireRow, _
.Columns(didd).SpecialCells(xlCellTypeBlanks).EntireRow, _
.Columns(didd))
.FormulaR1C1 = "=rc[" & dd - didd & "]+7"
End With
On Error GoTo 0
End With
End Sub