How to process payment for the supplier on behalf of another supplier..

Hello,

We have a requirement where we are dealing with one  of our sister company as a Supplier & entering prepayments as payments for setup charges...now we have incurred some expenses with another supplier on behalf of our sister company supplier & we want to pay for this expense to the actual supplier on behalf of our internal supplier...in other words

suppose we have tho suppliers Supplier A & Supplier B

Supplier A is our sister company to whom we are treating as a supplier

Supplier B is normal supplier who is providing services to Supplier A

Supplier B has provided some services to supplier A for which we want to process payment to supplier B on be half of supplier A...