C# - Press A Button On A Different Process (nunit.exe)?

I have recorded this macro that attaches to a process (nunit.exe) for me. Now I'd like to press a button (named "Run") on the window of the process I am attaching to, but how? I have recorded this macro:

Sub DebugNUnit()
DTE.ExecuteCommand("Tools.ExternalCommand6")
'need a short delay for nunit process to appear in process list:
Threading.Thread.Sleep(200)

[Code]...

I am using nunit 2.5.7 and for attaching and debugging to work you need to attach to the nunit agent and press run on the nunit gui, for more recent versions of nunit you can attach to the nunit gui.the above script enables nunit debugging from the Visual Studio IDE with just visual Studio and the nunit binaries. all you need to do is set up nunit as an external tool (with the current project as a parameter), create a custom toolbar, and add a button to that toolbar that uses the above script. this will start nunit, attach to it, start running the tests, and break at your breakpoint.

one more thing: in the nunit gui disable "Save Visual state of each Project" in Tools -> Settings -> Tree Display or the nunit gui will remember the last run test, which is a pain if that's not the one you wanted to debug.