So to create a formula to solve your problem, go to the errors worksheet and put this in cell A1:

=MATCH(PM!C1,INDIRECT("PM!

Then put this in B1:

=IF(ISNA(A1),IF(PM!C1="","

If you copy these down to match the number of entries you have in your PM worksheet, then you should see the word blank wherever there was a blank in column C and a number wherever any number was found below it in the list. You may want to hide column A in the errors tab since it's a "work" column.

If this is not sufficient, I can write something in VBA for you.