allocate wan interface for ipsecVPN

Dear Sir or Madam,

I need some help:

This is our situation:
Location A has two DSL lines (25mbit).
Location B has one gigabit connection with one IP-Adress.

I need the following configuration options:
the first line of A should establish a ipsec VPN to location B.
and the second line of A should establish a ipsec VPN to location B, too.
After this I want to configure a Bonding over both ipsec VPN ´s.

I can´t find the configuration where I can adjust that the first ipsec VPN takes the first line and the second ipsec VPN takes the second line. It´s important to establish the connection from site A (NAT in use).

Could you please tell me a solution for this requirement?

Thanks a lot.