Dynamic List for Dropdown box

Hi,

I had some help previously with a formula and I am trying to amend it to work on an additional list.

I have a box and based on that condition I would like a list populated.

e.g. In cell E24 the user selects the division which populates a number. This number (in cell G4) needs to be used as a lookup. Anything on the sheet "Activity Types by Network" with that code in column A the description needs to be returned to the help sheet.

The code I am using (doesnt work) is:

=IF(ROWS(A$1:A1)>COUNTIF('Activity Types by Network'!$C$2:$C$50000,$G$24),"",INDEX('Activity Types by Network'!$A$2:$A$50000,SMALL(INDEX(('Activity Types by Network'!$C$2:$C$50000=$G$24)*(ROW('Activity Types by Network'!$C$2:$C$50000)-ROW($D$2)+1),),COUNTIF('Activity Types by Network'!$C$2:$C$50000,"<>"&$G$24)+ROWS(A$1:A1))))

Which element is wrong? The list is to go in column V of the helper sheet

Paul