GST Refund - Agreement to refund the GST amount back to the service provider

Can a service provider require the client to enter into a contract stipulating that the client will refund the GST amount to the provider after the client has successfully claimed the refund from the GST department?  

Does the GST framework permit a contractual arrangement whereby a client agrees to refund the GST amount to the service provider after the Client has claimed the refund from the GST department?