conversion exit for Material number conversion from R/3 to APO

Hi,

Can anybody tell me conversion exit (function module) for Material number conversion from R/3 to APO in R/3 system. I mean i have 18 digit R/3 material number which i have to convert to 40 digit APO material number in R/3 system.

Please suggest to win full points.

Thaniks in Advance,

Chandan Dubey