stock keeping unit -issue

Dear Jurgen,

SAP technically requires that the base unit of both material is equal.

if that is not the case, then do a goods issue of material A with movement 201 and do a goods issue cacellation at material B with movement type 202. Just keep in mind that the material value is not flowing from A to B, you issue value from A, but you receive with value of B and you may need to adjust the price with MR21.

you have given the above solution for the subject issue.I am not able to understand your solution(workaround).Can you please give more clarity?