Replication Question

I have a sql server. The publisher is setup to use distributor 'A'. There are several publications that use this distributor. I have created a publication. I want this publication to use a different distributor ('B'). When I try to set up a new Push Subscription, I am defaulted to distibutor 'A' and I need to use distributor 'B'.

Can anyone tell me how I can configure this publication to use a different distributor to I can set up the Push Subscription?

Thank You,

Robert