Exclude Condition Type

Dear Gurus,

I have the following pricing mechanism

step 10. PROO

step 20. ZLOD (mark statistical)

step 30. ZDIS

Sub total   10-30,

i want that statistical condition type value cant be add in the subtotal, what routine i should assign on it.

as hte rest of the mechanism of the above pricing procedure is very complex thats why i cant place the step 30 (ZDIS) on step 20 (ZOLD), to get the right calculations.

please reply.