Not able to sum the field in Crystal reports 9 formula editor

[sathyguy]

Friends,

The below formula is not working. Please point me where iam making mistake.

whileprintingrecords;
global numbervar tottrd;
numbervar cnttottrd;
if 
(
{Admin.OTC}="001"
or 
{Admin.COEN} in 
["Chargeable Labour + Chargable Spares",
"Chargeable Labour + Free Spares",
"Chargeable Spares + Free Labour"]
)
then
cnttottrd := {PAYMENTS.PAIDAMT}
else
cnttottrd := 0;
tottrd := tottrd + cnttottrd

if i change
cnttottrd := {PAYMENTS.PAIDAMT}
to
cnttottrd := 1
then its working.......

Please treat this as urgent.

Thanks & Regards
Sathyguy