Days Calculation...

Hi all,

Need help in calculation of days between two dates that too with conditional.

Today ()

Invoice date

Receipt date

I want to find the number of days with condition like 

if receipt date is empty =current date - invoice date 

If receipt date is there =receipt date - invoice date

can we club these two with conditional in one formula.

I tried with =If condition eg =If(receipt_date =" ", current_date - invoice_date, receipt_date - invoice_ date)

Requesting your suggestion please.

Thanks in advance to all.