Setting Dynamic Ranges in VBA - excel

Question

I have the following code below. Instead of using stagnant ranges (i.e., Range("AF9:AF50") & Range(AK9:BI50")) I'm looking to implement a dynamic range that runs the code starting at row 9 through the last row of data for those columns. I've been reading on how to set dynamic ranges but I can't get it to work. Any advice/assistance is greatly appreciated.
Private Sub Worksheet_Change(ByVal target As Range)
Dim cell As Range
Dim controlRng As Range, nRng As Range
Set cell = Range("AK9:BI50")
Set controlRng = Range("AF9:AF50")
Set nRng = Intersect(controlRng, target)
Application.EnableEvents = False
If Not nRng Is Nothing Then
Select Case target.Value
Case "No Promotion"
target.Offset(, 1).Value = Range("M" & target.Row).Value
target.Offset(, 4).Value = Range("P" & target.Row).Value
target.Offset(, 9).Value = ""
Case "Promotion"
target.Offset(, 1).Value = ""
target.Offset(, 4).Value = ""
target.Offset(, 9).Value = 0.07
Case "Demotion", "Partner", ""
target.Offset(, 1).Value = ""
target.Offset(, 4).Value = ""
target.Offset(, 9).Value = ""
End Select
End If
If Not Application.Intersect(cell, target) Is Nothing Then
Select Case target.Column
Case 37, 39, 43
target.Offset(, 1).Value = target.Value / Range("V" & target.Row).Value
Case 38, 40, 44
target.Offset(, -1).Value = WorksheetFunction.RoundUp((target.Value * Range("V" & target.Row).Value), -2)
Case 41, 60
target.Offset(, 1).Value = WorksheetFunction.RoundUp((target.Value * Range("V" & target.Row).Value), -2)
Case 42, 61
target.Offset(, -1).Value = target.Value / Range("V" & target.Row).Value
End Select
End If
Application.EnableEvents = True
End Sub

Answer 1

I'm assuming your problem is dealing with the letter aspect of ranges and trying to make that dynamic? If so the syntax you may be looking for is.
Set MyRange = MySheet.Range(MySheet.Cells(TopRow, LeftCol), MySheet.Cells(LastRow, RightCol))
So For example, these two ranges will be equivalent but the first can be generated dynamically.
TopRow = 1
LeftCol = 2
LastRow = 100
RightCol = 3
Set MyRange = MySheet.Range(MySheet.Cells(TopRow, LeftCol), MySheet.Cells(LastRow, RightCol))
Set MyOtherRange = mysheet.range("B1:C100")
There are several methods to find the last row of a column, some work better in other circumstances then others. Look here https://www.thespreadsheetguru.com/blog/2014/7/7/5-different-ways-to-find-the-last-row-or-last-column-using-vba
I usually use this
LastRow = sht.Cells(sht.Rows.Count, ColumnNumber).End(xlUp).Row

Answer 2

If I understand the question correctly, the columns and starting rows are static and only a dynamic last row reference is needed.
In Worksheet_Change event:
Set cell = Range("AK9:" & LastRow("BI"))
Set controlRng = Range("AF9:" & LastRow("AF"))
Choose a row number larger than any number of rows your data will likely have (e.g.1000). Then, in the same module:
function LastRow(strColumn as string) as long
LastRow=range(strColumn & 1000).end(xlup).row
end function
VBA will re-calculate the LastRow every time the Worksheet_Change event is raised,
thus making your ranges dynamic.