If you're using Excel 2007 or later you can use the IFERROR function:

=IFERROR(INDEX(INDIRECT("'"&A4&"'!$CW$112:$EA$163"),MATCH(B4,INDIRECT("'"&A4&"'!$b$112:$b$163"),0),MATCH($T$ 2,INDIRECT("'"&A4&"'!$Cw$7:$ea$7"),0)),0)