Looking for help or help for hire – pull value out of a query string in a url

Hello,
I need some help and I am willing to pay if necessary. If there is a better place to post this, please direct me to the site/forum. I have a WordPress powered site running the Studio Press, Life Style theme. My question has nothing to do with the theme or out of the box WordPress functionality.

We use a third party SaaS which can send an email distribution with a link that sends users to specific page in the SaaS and auto log the user in. The SaaS provides us with a website, but it is very out dated in regards to the look and feel. So I’ve embedded the SaaS website into WordPress.

I’ve been sent the following from the SaaS, which I need to pull off with php in WordPress.
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In order for us to push the appropriate page back to your frame (ie, action alert), you need to be able to accept our querystring in the URL to load the appropriate page. When a user clicks the link from an action alert, it will immediately redirect back to the your frameset. We will pass an HTML-encoded URL in the querystring so the you can pull in the correct page.

Example:
https://yoursite.org/eAd.aspx?framesrc=https%3A//www.OurSite.com/gr/WebPublish/controller.aspx%3FSiteName%3DYOURSITE%26Definition%3DFedHome%26SV_Section%3DFederal
Your frame page will look for “framesrc” in the querystring, and pull that URL into their page.
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Any advice would be greatly appreciated.
Thanks!
–Perry