PO Basic price in case of dealer

Hi,

As per the process for procurement of material from delaler as the tax amount which dealer will pass on is not exactly know at the time of PO it is depend upon the which excise invocie amount the dealer willl pass, so in presetn we are modifying the PO price after getting invocie from dealer know as in case of delaer the basic price should be the base price + all tax amount then in capture excise invoice we split the base amoun and the tax amount by first selecting the MRP indicator now for below case

Actual base price : 100

Taxes amount which delaer have pass is aroung 12 rs , now in our PO for material the base prie is added as 112 then it is plited in capture excise invoice, then only the base prices 100 is updated in GR/IR account, but whenever we check in ME2M or ME1P the material base price system shows as 112 , our user want that the base price should be 100 because othere amount is tax amount.

How we can map this.

regards,

zafar