dear sir
you can use alternative material group and assign only one material with usage probability 100% and strategy 2 (100% check ) and priority 1 as below Pic :
alt group priority strategy usage probability
mat 1 1 1 2 100 %
mat 2 1 2 2 0%
mat 3 1 2 2 0%
mat 4 1 2 2 0%
system will chose only one material and put it in production order .
Refer below links. You will get the idea.
http://scn.sap.com/docs/DOC-52036
http://scn.sap.com/docs/DOC-49355
hint ##the upper two Pic's copied from the second reference doc.
Regards,
nassar