MRP cumulative proposal

Dear Guru's,

1. my scenario is, i have FERT material Aand B, for both i use HALB material C.

2. i will put PIR for A and B in the same day and i run MRP.

3. After MRP run system creates proposal for A, B and for C which is ok, but for is it is different proposals wrt to A and B.

4. My requirement is i should get one proposal per day for C by cummulating all requirements of the day. What is settings required for this? please can anyone tell me

sree