making calculation field blank

[KLA]

I have this field "A" with a calculation:

Case(IsEmpty(Override), Round(Payment Amount - Programming Billing::Monthly Commission,2),Override=0,TextToNum(""),Round(Override,2))

Sometimes i put a value in "Payment Amount" but i don't want this calculation field "A" to calculate. I only want it to if there is a value in "Monthly Commission" as well. I have an override field over "A" that i can put a "0" in and it becomes blank. The problem is that i use this field in another calculation (which i also want blank) and it doens't recognize the override and use that instead of the calculated amount.

Any ideas how i can make my calulation only work if there is a value for ALL fields involved?

[Chuck]

How about this?

Case(