Reach PSTN line using IVR

Greetings to everyone, this is my first post on the forum.
I have successfully setup Fee PBX, and I am currently running five extensions and two trunk. Two extensions and trunks are on a Spa3102 voip gateway. I followed the instructions of a previews post to set the dial plan options up, I have no problem with them. The other three extensions are on computer soft phones.
I have also setup an IVR sucessfully, and can reach all my internal extensions from trunk #1. My problem is that I want to reach trunk #2 using the same IVR. Trunk #2 will be on an external location (different ip address), and the IVR settings only allow extensions. What is the simplest way about solving this problem??
Is there any way to dial an X number to reach my trunk and then dial an external number?

Thank You,

Juan P

On your IVR, set up a hidden choice for a DISA. Set up the DISA and make sure you secure it. That should do it.

Thank you so much. Right after i posted this yesterday, I found that I could get an internal dial tone by using DISA. I had the right ideas but could not put them all together.

Thanks again,

Juan Perez