Hi,
Keeping with the VLOOKUP() theme you are using, to return a null string "" in Excel 2003:
Code:
=IF(ISNUMBER(MATCH(K12,Events!$A$2:$A$2000,0)),
VLOOKUP(K12,Events!$A$2:$D$2000,4,FALSE),"")
If you want it to show a "-" when a match isn't found then
Code:
=IF(ISNUMBER(MATCH(K12,Events!$A$2:$A$2000,0)),
VLOOKUP(K12,Events!$A$2:$D$2000,4,FALSE),"-")
In Excel 2007 things are easier because there's a new function introduced called IFERROR() which can do this sort of thing more succinctly.
Hope that helps...