Frankly, I didn't fully understand your request - however, you may try:
=TODAY()-D5
while using the "1904 Date System' ['Tolls' 'Options' 'Calculation' tab]
Micky


"Chris" wrote:

I am trying to calculate days past due. For and invoice tracker.
I have C5=date invoiced/D5= Payment due/ h5=days pat due.
I need a formula to calculate total days outstanding.
I thought =(D5-C5)-Today() but this is not working.