Payment with different currency

Hi,

I want to know how this will handle in PeopleSoft.

My Base currency AP and PO business unit are USD. I want to pay vendor with different currency.

1) Created a PO with $ 100.

2) Create a voucher using copy PO function and voucher created with $ 100.

3) I want to pay to vendor in GBP currency. If I change the currency to GBP and payment will created with GBP of 100. But i want system automatically convert and pay the amount.

4) how system will convert to using exchange rate of 1 USD = 1.5 GBP. In that case payment should be paid 150 GBP.

Can you please let us know how to pay the amount with different currency with out changing the gross amount and changing only Currency.