Try this:

=if(isna(VLOOKUP(A2,WAUKREF!A2:S1000,18,0)),0,VLOO KUP(A2,WAUKREF!A2:S1000,18,0))

+if(isna(VLOOKUP(A2,WWREF!$A$2:$S$1000,18,0)),0,VL OOKUP(A2,WWREF!$A$2:$S$1000,18,0))

Should give you what you want - the lower case will convert to upper
case once you type it in.

Hope this helps.

Pete