I get an 'you've entered too many arguements' error message with my formula
below. What do I need to do to get it to work?

I have 2 tables, PR and nonPR, and I want to add values together where the
left most strings match in each. If only one table contains the string then
take that value, if neither do then return a blank.

=IF(ISERROR(VLOOKUP(K16,pr,3,FALSE)),if(iserror(VL OOKUP(K16,nonpr,3,FALSE)),"",VLOOKUP(K16,nonpr,3,F ALSE)*1000,if(iserror(VLOOKUP(K16,nonpr,3,FALSE)), VLOOKUP(K16,pr,3,FALSE),VLOOKUP(K16,pr,3,FALSE)+(V LOOKUP(K16,nonpr,3,FALSE)*1000))))