Material Determination

Hello,

I have two material Material A and Material B. I have created condition table and attached that to access seq which is in turn attached to PP. PP is attached to Sales document type. I have mainatined condition record for the replacement of material.

I am using substitution reason 0004.

Material A - 10 (say) in stock -old material

Material B - 20 (say) in stock - new material

I have to replace Material A with Material B only after consuming Material A completely.

I have tried all permutation and combination. Can any one suggest a way?

Regards,

Kishore