Update Reserved Quantity at Batch Detail level

We are using OPM Batch mfg. and MES products for a pharmacy client. For a specific requirement relating to tolerances setup in MES for items that can be dispensed (pre-weighed) we want to be able to update the 'Reserved Qty' field in the batch detail (for dispensable ingredients) based on a pre-defined tolerance in the dispensing setup. For e.g. in the MES dispensing setup, the higher tolerance is set to 1.5, so we want to have the 'Reserved Qty' default to 'Plan Qty x 1.5' on the batch. We don't want users to manually go and update it. This way