I have a VLOOKUP that checks the information of 2 cells against a table to
determine the proper information to be displayed. It works fine except when
there is not any information yet placed in the cells. The that #NA shows up
when I just want it to be blank. I tried the ISNA, but I think I am doing
something wrong because I am getting the Error "You Have Entered Too Many
Arguments For This Function"

Here is my function. What am I doing wrong?
=IF(ISNA($B12<$O$12,VLOOKUP(C12,$K$14:$O$18,4,FALS E)),"",VLOOKUP(C12,$K$14:$O$18,5,FALSE))

It works fine if I remove the (ISNA and the ),"" piece.
Help me