2 ISP and pptp server

Hello! I have a dual wan configuration on RB951
Example:
ether1=ISP1 (IP 1.1.1.1)
ether2=ISP2 (IP 2.2.2.2)
ether3=LAN
remote ppptp client (dynamic IP)

And i have 2 default routes to 0.0.0.0/
ISP_1 have distance=2
ISP_2 have distance=1
so by default all traffic goes through ISP2


I create PPPTP server on RB951 and trying to connect from remote ppptp client (with dynamic IP) to ISP_1 IP (1.1.1.1)
In Torch I see incoming connection on ether1 (ISP_1) from 3.3.3.3 but there is incoming traffic only.
Seems it’s because outgoing trafic trying to go through ISP_2 (ether2) ?

So can you help me please.
What rules I should create to make PPTP connection works through ISP_1.
My suggestion - If client connect to ISP_1 IP - then all trafic to/from this client should work through ISP_1. and if client connect to ISP_2 - all traffic through ISP_2
Thanks!