Charge (Item) and Dimension on PO

Yashojit_Pandhare

I have Items for which Brand is set as a Dimension (Same code)

I created a PO as:

Item1 Brand A
Item2 Brand B
Item3 Brand B

on the same PO I added a Charge (Item) line for Freight charges which i want to distribute on the above items in proportion of Amount.
After assigning the Charge (Item) freight on the above item lines, while posting system prompted me to select the dimension Brand A for freight. Upon selecting Brand A, system prompted me to select Brand B.
I understood that, system is making value entries/adjustment entries for the Charge (Item) distributed on the above items and for each adjustment line would be requiring the appropriate dimension.

So as a solution i recreated the Charge (Item) lines splitted in two, with proportionate amounts which i had to calculate manually, for the two brands mentioned above as:

Charge(Item) Freight Brand A
Charge(Item) Freight Brand B

now i assigned the first line to the item line with Brand A and second line to the two item lines with Brand B and posted the PO.
The PO got posted successfully.

But doing this is an arduous task. Say if i have items with ten different brands in the same PO, i will have to calculate and insert ten different Charge (Item) lines and assign them to items with respective brands and the end-user also may not agree to this.
Is there some other solution to this?