Best way to prevent an item to be entered in a quantity (EA) which is not a multiple of a box (BX)

Dear all,I think that one way to achieve that purpose would be to create an mandatory adjustment in the schedule using quantity level break but we can not define "bracket quantities" :For instance, Item A  from 12 to 12 EA, 24 to 24 EA, ....you can enter only a "from quantity" (12  EA) to the next  "from quantity" (24 EA) so, all values included between 12 EA and 24 EA being accepted, the adjustment is present...I'm not sure to have been clear enough...Maybe an other workaround could be used rather than in advanced pricing.