use projects from other solution for debugging and enhancing code

Hello,
I use Visual Studio 2008 and work in two projects a (base) and b (myApp) in different solutions.
To work I add a reference a.dll to the b-solution.
I want to debug into a code which is working when i open the corresponding .cs file in b-solution.
But changing a-code is not quite usable. I always have to open the a-solution, change, compile, goto b-solution.
Is there a way to use an a-project reference in b-solution, and when i change a-code to compile it and use it in b solution with one step ?
thanks

If you want to run your project without errors, first build/rebuild to accept all the changes you are changed.

If I understand, then one thing that would help is to execute Visual Studio a second time so you can edit both projects without closing one.