How to not sum the null amount

[AlreadyLost]

Hi.. I have a Total Payment Formula that contain the following formula:
{#hazPMTAmt}+{#UstPmtAmt}+{#CalRisPmtAmt}+{#CalAdmPMTAmt}

Problem..
When I display the result it is blank.. I think it's because some of these amount is null. How can I modify my report to display the total amount?

 

[lbass]

Change the formula to:

(
if isnull({#hazPMTAmt}) then 0 else {#hazPMTAmt}
) +
(
if isnull({#UstPmtAmt}) then 0 else {#UstPmtAmt}
) +
(
if isnull({#CalRisPmtAmt}) then 0 else {#CalRisPmtAmt}
) +
(
if isnull({#CalAdmPMTAmt}) then 0 else{#CalAdmPMTAmt}
)

-LB