Please assist.

There are several things I am trying to accomplish.

1) I am trying to count the blanks in several columns for each sheet.
2) I would like to count all the dates in a column.
3) I have a function that gives me the last row for every sheet. However I
would like to get the last row number to use in the sumproduct cell
reference.
for ex. sumproduct(j24:lastrow)


I tried the below to count the blanks in 2 columns.
What have I done wrong?


wsNew.Range("f7").Value =
Evaluate("=sumproduct((F25:f136=ax3)*(j24:j136="") )") +
sumproduct((F24:f2650=ax1)*(k24:k2650=""))")

Thanks