Restrict values for characteristics in classification tab

Hello all,

characteris description can be assigned to a material with transaction mm02, in the "Classification" tab for batch management. Later when we do a goods receipt (MB01) against a purchase order with this material, we will enter the values for these characteristics.

My question is: how can we restrict the values for these characteristics, meaning for example only values lower than 1% are allowed to be entered at the goods receipt?

Thanks

Anne