Hi Vishal,
Without looking at it any closer, I'd guess you're running into an encoding problem. DIAdem 9.x saves VBScript files by default in Unicode, not ANSI. Depending how you are calling the VBScript from within your DataPlugin, this could be a stumbling block.
Note that you can change a SCRIPT panel setting in order to save VBScripts with ANSI encoding. Or you can read out every other byte from the VBScript file before running it with the Execute function.
Let me know if you need more info,
Brad Turpin
DIAdem Product Support Engineer
National Instruments