You can put the worksheet name directly in the VLOOKUP:
=VLOOKUP("abc",'Sheet1'!A1:C10,3,FALSE)
You can also take the sheet name from another cell, say E1.
=VLOOKUP("abc",INDIRECT("'"&E1&"'!A1:C10"),3,FALSE)
In this second formula, VLOOKUP will look in the range A1:C10 on whatever
sheet is named in cell E1.
--
Cordially,
Chip Pearson
Microsoft Most Valuable Professional
Excel Product Group
Pearson Software Consulting, LLC
www.cpearson.com
(email on web site)