Declare Form From Another Project?

Hi,

I have an app with 2 projects in it.
From the 2nd project form, I'm trying to set something off on the first project form, and so need to declare the first form (it is already set to public, but not sure if this is enough).

I have tried declaring as if it was a form within the same project, but that doesn't seem to do it?

Is it possible? Sorry if it's got a real easy solution, I'm still getting to grips with VB.

Thanks

I believe that you need to add a reference to your project that contains the form you want to access to your source project.

I tried that but it wouldn't let me because "an assembly must have a dll extension to be referenced."
I thought maybe I was refernencing it wrong.