<This is causing problems elsewhere>

It shouldn't. Don't use ISBLANK(A1), use A1=""

Please don't keep starting new threads - it just tends to fragment any
answers you get, and to waste the time of those answering questions that
have already been answered.

If C24:C29 are calculated values, then put something like this in the
worksheet code module (right-click the worksheet tab and choose View
Code):

   Private Sub Worksheet_Calculate()
       With Range("C24:C29")
           If Application.Count(.Cells) > 0 Then
               Range("C30").Value = Application.Sum(.Cells)
           Else
               Range("C30").ClearContents
           End If
       End With
   End Sub

If the values in C24:C29 are manually entered, use the Worksheet_Change
event instead - something like:

   Private Sub Worksheet_Change(ByVal Target As Excel.Range)
       With Range("C24:C29")
           If Not Intersect(.Cells, Target) Is Nothing Then
               If Application.Count(.Cells) > 0 Then
                   Range("C30").Value = Application.Sum(.Cells)
               Else
                   Range("C30").ClearContents
               End If
           End If
       End With
   End Sub

In article
<20800e76-969f-46c2-a75f-405a5ae459b7@p69g2000hsa.googlegroups.com>,