This is another one of those "Posted here for MY convenience" tips.
You can use the Visual Studio Debugger to debug a .vbs (vbscript) file executed with cScript.exe by using the //X flag at the command line.
To debug MyTest.vbs
cscript.exe MyTest.vbs //X
The //X will set a breakpoint and invoke the "select a debugger" dialog where you can choose Visual Studio and step into your vbs code. I haven't found a way to directly edit from the debugger however, so I end up having to debug, break execution, fix my bug and restart the vbs script file again to see my changes.