Hi Keith,

You could wrap your procedure in an If...Then block so that it only
processes non-empty columns.

Also, to find the last row in a column you should work from the bottom
upward. If there are empty cells between the last row and first rows, use
another If...Then block to skip the blanks.

Example: (assumes you are iterating through each cell in the range)

Dim c As Range
Dim lLastRow as Long

lLastRow = Range("AI" & Rows.Count).End(xlUp).Row

If lLastRow 2 Then 'enter the procedure
For Each c In Range("AI2:AI" & lLastRow)
If Not c = "" Then 'continue

'do stuff

End If
Next c
End If

Note that I used an empty string for the test so that it includes cells with
formulas that return an empty string. (using IsEmpty will include such a cell)

HTH
Regards,
Garry