Docker networking - "forcing local machine use same source port as docker container"

I have a docker container A from which i am trying to send a packet to a destination C which is outside of my local network B
IP addresses of all the systems
A -
B -
C -

To able to reach C from B i have connected my local system to VPN
When i try to send a packet from A to C(for example RTP), A chooses one source port and send the packet from that source port but first that packet reaches to B and then B forwards that packet to C . Now when B forwards the packet it doesn’t use the same source port as used by A but uses a random source port

So is there any way to force the same source port used in A also in B