Batch internl number assignment

Hello SAP gurus,

Lets suppose i have finished product, semifinished product and raw material with me.I am managing all of them in batches.I want to use automatic creation of batch (internal number assignment) for them.Now my question is i want to use different number ranges for all of them.

Currrently its using the same number range for all of them.Suppose if i created one production order for semifinished product than its giving it batch no. 0000001.Again if i create production order for finished material than its giving it batch no. 0000002.

I want different number ranges for both of them by internal number ranges only.

plz guide me in solving this problem.