Dynamically adjust range based on last column in vba - excel

Question

I have a table in excel where i am inserting some column, because of that last column is getting changed, I have to detect the last column and set it as a range in vba
I have written code to find the last column and convert it to alphabet, however i am not able to set it as a range.
Public Function ColumnLetter(ColumnNumber As Long) As String
ColumnLetter = Split(Cells(1, ColumnNumber).Address(True, False), "$")(0)
End Function
Dim Rng As Range
Dim LastColumn, LastRow As Long
Dim Str As String
LastRow = Cells(Rows.Count, 2).End(xlUp).Row
LastColumn = Cells(2, Columns.Count).End(xlToLeft).Column
Str = ColumnLetter(LastColumn)
'Set Rng = Range("M7:M" & LastRow)
I want to write Commented line as
Set Rng = Range( & Str & "7" & LastRow)
To make it dynamic
How can i do this?

Answer 1

First, change Str to something else; you're shadowing the Str function.
Dim colLetter As String
colLetter = ColumnLetter(LastColumn)
Then concatenate as necessary:
Set Rng = Range(colLetter & "7:" & colLetter & LastRow)
Note that you can skip using the column letter and just use Cells with the column index.
Set Rng = Range(Cells(7, LastColumn), Cells(LastRow, LastColumn))

Answer 2

As others pointed out, Str isn't the best variable name. Let's say you change it to "ColLtr" ... then your specific answer is Range(ColLtr & "7:" & ColLtr & LastRow)
However, might I suggest another tack?
If you are trying to set the range as the lower right corner of the used range, use:
With {sheet}.UsedRange
Set Rng = .Cells(.Rows.Count,.Columns.Count)
End With
(substitute {sheet} with WorkSheets("MySheet") or ActiveSheet or however you prefer to specify the worksheet.)
If you need the entire column, adjust it to:
With {sheet}.UsedRange
Set Rng = .Columns(.Columns.Count)
End With
BUT ... if you "Format Range as a Table" (creating a ListObject), you can bypass VBA altogether and use [TableName[ColumnHeader]], either in VBA or in your worksheet formulae. Of course, "TableName" and "ColumnHeader" would be specific to your table's name and the actual text in your column header.