When you implement a simple VBScript function, you can display test messages using the VBScript "MsgBox" command. Example:

Function test(s)
     MsgBox(s)
EndFunction

You call the VBScript function in GuiXT with:

CallVBS test "Hello"

and receive the following small popup on your screen:

 

During the development of more advanced VBScript functions you will certainly prefer to work with a professional debugger tool. Microsoft provides the "MS Script Debugger" free of charge, or you can use a version of "MS Visual Studio" if this is needed for other development projects such as developing your own VB.Net controls. If no special script debugger is installed on your PC, the debugger that comes with Internet Explorer will be used.

To invoke the debugger you put a "Stop" command into your script:

Function test(s)
     Stop
EndFunction
 

When the "Stop" is reached, the system sends a popup screen that depends on the installed debugger(s):

You select a debugger (if several are installed) and start the debug session:

Please note: If you have disabled script debugging in the Internet Explorer setting:

Internet Explorer -> Extras -> Internet Options -> Advanced

the "Stop" command will simply stop processing the script, without a message and without a debugger coming up: