VBA referring to a different sheet, automatically fill cell based on content of other cell

No sir, it will be brought over from the For Sales tab when you hit the Copy Data button on the itmof tab.

Place this code in the worksheet module for Sheet("itbof")... not in Sheet("itmof"). When you click the 'Copy Data' button and then select Sheet("itbof"), your columns should automatically update.

Private Sub Worksheet_Activate()
    Dim bottomA As Integer
    bottomA = Range("A" & Rows.Count).End(xlUp).Row
    Dim bottomL As Integer
    bottomL = Range("L" & Rows.Count).End(xlUp).Row
    Dim rng1 As Range
    Dim rng2 As Range
    For Each rng1 In Sheets("itbof").Range("A2:A" & bottomA)
        If rng1 <> "" Then
            Cells(rng1.Row, 3).Value = "A"
            Cells(rng1.Row, 20).Value = "N"
        End If
    Next rng1
    
    For Each rng2 In Sheets("itbof").Range("L2:L" & bottomL)
        If rng2 <> "" Then
            Cells(rng2.Row, 9).Value = Cells(rng2.Row, 12).Value * 1.08
        End If
    Next rng2
End Sub

OK, I'll rephrase this, I did some more testing, and the only time it errors out is if I switch over to the itbof tab before I hit the copy data button, other than that it works great. To make it "dummy proof" is there any way to just make it run after I hit the itbof tab? This way it doesn't matter if we accidentally switch to that tab first before the copy data button is pressed...

Thanks, I appreciate everything you've done so far!

I would like to make a suggestion. First, remove the code from the worksheet module and put it into a regular module and change the name of the macro so that it's not a Worksheet_Activate event. Then you can run the macro by assigning it to a button on either worksheet or you can call the macro from your "Copy Data" macro. If you call it from the "Copy Data" macro, it will complete the "itbof" sheet automatically when it completes the "itmof" sheet. If you want to keep the two tasks separate, then assign it to a button. I hope that helps.