Trouble with Report in Browser

I'll try to make this clear and concise. I have a report that has 2 required parameters. When run from the Reports site, the user picks the first parameter, then the browser refreshes with a drop-down list populated with values that are dependent on the resultset from the first parameter. This all works perfectly, until I want to call the report from an outside application.

The 1st drop-down list is populated from a dataset with all Load Numbers.
The 2nd drop-down list is populated from a dataset with Order Numbers associated with that Load Number.

Do do this, I have to use the ReportServer site. It works from here too when I pick a Load Number from the drop-down list, or when I manually enter the first parameter into the querystring (address bar) with something like: &MyLoadNumber=9999

The report will load correctly when I choose the 2nd parameter from the drop-down list and click the View Report button.

The problems creep in when I add the second parameter on the querystring like &MyOrders=BR549 - The browser goes out and gets the report, but what I get back is the report asking me for the 2nd parameter, even though it is right there in the querystring!

I know it is a problem that the 2nd parameter isn't requested until the 1st one is loaded correctly, and the dataset for the 2nd parameter has the 1st parameter as a required parameter for it.

If you are reading this and you know what I can do to solve this, please post a comment. I'll be sure to tell my boss you helped me! ;)