"Chris" wrote...
Here you go
=IF(SUMPRODUCT(--(COUNTIF(INDIRECT("'"&WSlst&"'!K5:K20"),Q5)0)),
INDEX(WSlst,MATCH(TRUE,COUNTIF(INDIRECT("'"&WSlst &"'!K5:K20"),Q5)0,0)),
"Not Found")

For this to return #N/A, either the first or second argument to IF would
need to evaluate to #N/A. The only way the first could do so would be if one
of the entries in WSlst itself were #N/A. What's the entire contents of your
WSlst? You should type the formula =WSlst, press [F9] which will evaluate
WSlst, copy the result to the clipboard, and paste into your response. If
there are any #N/A entries in it, that's the problem.