Complex routing question

Hello people,

Please help me if you can. Let me explain the situation.

I have the following scenario:

bridge1(192.168.1.0/24) — Mikrotik(192.168.1.254) — DSL Link(dynamic IP)
(10.36.143.197) — Router of Private VPN(10.36.143.193)

bridge1 has the following ports: ether2, wlan1

ether2 is the master port for ether3, ether4 and ether5

i have a pppoe dial-out interface on ether1, which gets a dynamic ip, thus i have a masquerade rule that masks every connection going out of interface pppoe1

i need every computer on the 192.168.1.0 network to access a system on 10.21.7.13, so i`ve created a static route on mikrotik to 10.0.0.0 with 10.36.143.193 as gateway

i can ping 10.36.143.197(mikrotik) from any machine on 192.168.1.0, but i cannot get to 10.36.143.193. Yes, i know, i need to have reverse route, but that is my problem. I dont have access to 10.36.143.193 router, its a ISP owned router and they wont let me access it to create a route, believe me, ive tried several times with their support and they are not friendly at all.

How can i mask every connection passing trought the mikrotik router, with destination to 10.x.x.x, to be masked as 10.36.143.197, so i don`t need to create a route inside 10.36.143.193 ?