I am trying to limit data entry options into a worksheet based on other
information already 'correctly' entered. Based on a number of criteria I
return a Named Range as a result of the formula:

I am using =INDIRECT(AC18) as the data validation formula

Cell AC18:
=IF(ISNA(IF(TubeRequired=VLOOKUP(SystemSelected,'I nput
Lists'!$A$3:$E$40,2,FALSE),VLOOKUP(SystemSelected, 'Input
Lists'!$A$3:$E$40,3,FALSE),IF(TubeRequired=VLOOKUP (SystemSelected,'Input
Lists'!$A$3:$E$40,4,FALSE),VLOOKUP(SystemSelected, 'Input
Lists'!$A$3:$E$40,5,FALSE),"Get
Quote"))),"",(IF(TubeRequired=VLOOKUP(SystemSelect ed,'Input
Lists'!$A$3:$E$40,2,FALSE),VLOOKUP(SystemSelected, 'Input
Lists'!$A$3:$E$40,3,FALSE),IF(TubeRequired=VLOOKUP (SystemSelected,'Input
Lists'!$A$3:$E$40,4,FALSE),VLOOKUP(SystemSelected, 'Input
Lists'!$A$3:$E$40,5,FALSE),"Get Quote"))))

The resulting named ranges in the 'InputLists'!$A$3:$E$40 are BracketList_A,
BracketList_B and BracketList_C where these named ranges containg the
brackets that are appropriate for selection by the user. These named ranges
are Dynamic Ranges allowing us to update the data table as needed.

Based on what I'd read in Debra Dalgleish's site and in the help files I
thought that this would work... I don't get any errors but the drop down
list in the data validation is empty.

Too much info?