no of days from OP_KEYDT

Dear ALL,

In  our cutomer outstanding report ,  which is using standard sap exit variable OP_keydt,op_keydt2,op_keydt3 .

Now we want , to have another coulmn NO of Days days passed since key date for each record.

Which is equal to the

no of days =  user input date (op_keydt) - netdate of the that records.

Can you please suggest how to acheive this.

thanks in advance.