Is there any debugger for NSIS?

I wanted to debug my script. Is there any good gui based tool for this.. (Like NSIS editor)

MessageBox + DumpState plug-in as Andrers said.

Actually this is good idea - have anyone tried to write debugger? Where to start?

I had some ideas on how to implement a debugger with my nsL Assembler (for my University degree). However it would have been a huge project in itself and I am no longer working on the project (nor plan to).

Stu