All three cells listed in the formula below are dates. If there is data in
cell R9, that cell should be calculated as below. If 01/00/00 is listed in
R9, the formula should calculate R4 in the same manner. I have started with
the following formula, but obviously have not incorporated in R4. Can anyone
help?

=IF($R$9-A73500,0,IF($R$9-A73<=0,0,IF($R$9-A730,SUM($R$9-A73))))