omitting blank cells

[seanrigby]

Formula does not take into account blank cells, and when I attempt to turn it into a percentage, it becomes greater than 100% if there is a blank cell.

Formula is as follows:

=SUMPRODUCT(('All Data sheet '!D$13:IV$13>=Print!$E$3)*('All Data sheet '!D$13:IV$13<=Print!$E$4)*('All Data sheet '!D14:IV14='All Data sheet '!$D$3))/SUMPRODUCT(('All Data sheet '!D$13:IV$13>=Print!$E$3)*('All Data sheet '!D$13:IV$13<=Print!$E$4))

What am I missing to omit the blank cells?