AP Invoice line additional costs

We have some purchased parts that have a charge added to them when we buy them, this can be different every time and we don’t know how much the charge will be until we receive the invoice.

Accounts wants the value to be assigned and given GL Code and entered on the AP Invoice line (as this is a part specific value). I have tried using Misc Charges on the Line but when it’s posted this always goes to PUR-VAR GL Code, this is because we have a Code assigned to part class.

Does anyone know if there any way to get this value to go to the correct GL code against the AP invoice line.

Thanks,

John