Date validation in a formula

[Scott63304]

How can I validate a cell contains a valid date before
using the value in a formula? For example: start_work_date
minus end_work_date = networkdays. Either date field can
have blanks, text or a valid date. If the field has blanks
or text, the formula returns a negative number
or "#value!". I would like to eliminate these results.

Suggestions?

Thanks
Scott

 

[Frank Kabel]

Hi
try
=IF(ISNUMBER(A1*B1),NETWORKDAYS(A1,B1),"")