Then just implement Jacob's suggestion, as in:
=IF(ISERROR(DATE(YEAR(A1),MONTH(A1),DAY(A1))),"",
SUMPRODUCT(--(Progress!$A$5:$A$1756=$A$5),--(Progress!$D$5:$D$1756=C$3),--(Progress!$E$5:$E$1756=$B5)))

Regards,
Fred.

"Ayo" wrote in message
...
I was looking for something in this line:
=If(A1=Date,
SUMPRODUCT(--(Progress!$A$5:$A$1756=$A$5),--(Progress!$D$5:$D$1756=C$3),--(Progress!$E$5:$E$1756=$B5)),
"")

"Jacob Skaria" wrote:

Please try this will return FALSE if valid date..
=ISERROR(DATE(YEAR(A1),MONTH(A1),DAY(A1)))

If this post helps click Yes
---------------
Jacob Skaria


"Ayo" wrote:

Is there a function like the ISBLANK function for dates. I am trying to
write
and IF statement formular that works like this:
If the value in A1 is a Date then perform calculation else leave
blank.

What is the best way to do this.

Thanks