VBA loop / do until

There aren't enough details to really write anything. But here's a tutorial/example of how to access data from seperate workbooks and how to write values into cells inside a loop.

The equation you were looking for where the output row # follows the pattern 1,2,3,2,3,2,3... is a little complicated with normal math, but it can be accomplished in programming math by using a Boolean expression as part of the equation.

Sub RowNumberer()
    Dim CountWB As Workbook
    Set CountWB = Workbooks("Your Count Sheet Workbook's Name (plus file extension)")
    
    Dim CountSheet As Worksheet
    Set CountSheet = CountWB.Worksheets("Your Count Sheet's Name")
    
    Dim CountSheetValue As Long
    CountSheetValue = CountSheet.Range("Cell Address of your Count result (3, 5, 7, 9)")
    
    Dim UploadWB As Workbook
    Set UploadWB = Workbooks("Your Upload Template Workbook's Name (plus file extension)")
    
    Dim OutputSheet As Worksheet
    Set OutputSheet = UploadWB.Sheets("The Name of the Sheet you want to number the rows on")
    
    Dim i As Long
    For i = 1 To CountSheetValue
        OutputSheet.Cells(i, 1) = i Mod 2 - 2 * (i > 1)
    Next i
End Sub

To explain the formula: i Mod 2 - 2 * (i > 1)

i Mod 2 is taking the iterating value i and retrieving the remainder after dividing by 2. This alternates between 1 and 0.

We would just need +2 in order to move that from 1 and 0 to 3 and 2. But we only want +2 after the first number since we want the first number to be 1.

So I added the boolean expression (i > 1) which is 0 when False and -1 when True. I don't know why True = -1 in VBA. So the term - 2 * (i > 1) is 0 when i = 1 and +2 when i > 1.