seek your help on MQ cluster - work load balance problem

I have 2 machines -     HostA (QmgrA)          and           HostB (QmgrB) ,

they join in the same mq cluster - clusterGW ,             also I have a cluster mqm - QmgrGW

and they can balance the jobs - i.e. Once there come 2 job messages from external host, 1 will handle by QmgrA, another 1 handle by QmgrB.

(As QmgrA is totally the same as QmgrB, that means they has same config, local Q, remote Q , etc)

Now I want to develop a WMB flow on both HostA and HostB 's broker servers.

The function of the flow will send out the job messages to QmgrA / QmgrB.

I want such flow can balance the messages - i.e. If the flow of HostA sends 2 messages, 1 can be sent to QmgrA while another 1 can be sent to QmgrB. The same for the flow of HostB .

But now the current situation is that - If the flow of HostA sends messages, the messages only can deliver to QmgrA  by 1st priority

(By 2nd priority the messages can deliver to QmgrB only if message failed to QmgrA .)

That means we cannot do 'work load balance' internally on QmgrA / QmgrB .