Check to make sure that your VLOOKUP function is correct.
I tested this, and it works to look for the value in A4 and match it to a value in A8:A13 and pull the corresponding number out of C8:C13
=IF(ISNA(VLOOKUP($A$4,A8:C13,3,FALSE)),0,VLOOKUP($A$4,A8:C13,3,FALSE))
My best guess is some kind of problem with the dat range. I always have problems with the named ranges, so I don't use them and can't give you any advice on that. Try it with a direct cell reference and make sure that it is working right like that, then try the named range thing again. My best guess is that dat got messed up and is not defined over the correct range. Like I said, I don't use them, so try the original
=VLOOKUP($A$4,dat,3,FALSE)
and see if you get the right answers, with the N/A
Then try it my way, see if it works right. If you are still having problems, post again. Good Luck.