#DIV , #VALUE VARIATIONS OF FUNCTIONS and CONDITIONAL FORMAT NOT CORRECTING ERROR

The formula that returns a #DIV error has been changed various ways to make it go away (based on functions from several other posts) but for some reason those suggestions and even the one for 'conditional formatting' did not work.

Would like to know why this particular function is being difficult and what part needs corrected?
=SUM(C5:C12)/C13 returns #DIV

Tried the following:
=if(xx="","",formula)
=IF(C13="","",C5:C12/C13) changes the #DIV to a #VALUE instead
=IF(C13="0","0",C5:C12/C13) returns a #VALUE
=IF(C13="","",(C5:C12/C13)) returns a #VALUE
=IF(C13="","",(C5:C12)/C13) returns a #VALUE

=IF(ISERROR(C5:C12)/C13,0,"")
=IF(ISERROR(C5:C12)/C13,0)

Thanks in advance for the guidance,
C.

In all your attempted resolutions, You're forgetting a critical part of the original formula
=SUM(C5:C12)/C13

So try
=IF(C13="","",SUM(C5:C12)/C13)

Jonmo, I tried the one you provided and still no luck..
Attached is a sample file for experimenting.

That's IT!! Thanks Norie!

I always use the code tag box with the VBA code but had not heard that the small functions/formulas also needed to be in a code window.