formula calculation when cells are changed

[TR]

Hi,
I am trying to perform a calculation based on Range b2 in a workbook.
However, I want the user to be able to change this cell and not have
to rerun the macro again.
I have an if...then statement that evaluates less than 60 and greater
than 30, then it evaluates less than 30, etc.

Is there a way I can do this?

Here is my codewith help from a very nice person!)

With ActiveSheet
For iRow = 2 To lngRow
If InStr(1, .Cells(iRow, 2).Value, "appw1d",
vbTextCompare) Then
If LCase(.Cells(iRow, 1).Value) = LCase(" Target
Renewal") Then
For iCol = 6 To 20
If Range("$b$2") + .Cells(iRow - 1, iCol).Value + .Cells(iRow - 1,
iCol + 1).Value < 60 _
And .Cells("$B$2") + .Cells(iRow - 1, iCol).Value + .Cells(iRow -
1, iCol + 1).Value > 30 Then
.Cells(iRow, iCol + 1).Formula =
"=VLOOKUP(""appw1d"",$f$1:$g$16,2,FALSE)*(1-$b$2-30)/30"
ElseIf .Cells(2, 2).Value + .Cells(iRow - 1, iCol).Value < 30 Then
.Cells(iRow, iCol).Formula =
"=VLOOKUP(""appw1d"",$f$1:$g$16,2,FALSE)*(1-$b$2/30)"
Else
..Cells(iRow, iCol).Formula = "=VLOOKUP(""appw1d"",$f$1:$g$16,2,FALSE)"
Next iCol
End If
End If
Next iRow
End With

Thanks for your help!