Check if Excel workbook is open using VBScript

I have a vbs script which writes to an Excel spreadsheet. To be able to save the spreadsheet I need to ensure that it is not already open.

Can someone suggest the best way to do this?

Some research:

• I tried to create a Word Tasks objects to show me all running processes, but on Windows 7 it only tells me whether Excel is running or not.
• Creating an Excel.Application object does not give me access to all running instances of Excel.
• I thought about opening the sprea开发者_开发问答dsheet for writing but the only way I can think of doing this is with the File System Object OpenTextFile method which does not seem to be the correct approach as the Excel file is a binary.

Any other ideas?

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Since the Excel.Application object doesn't give you access to all instances of Excel, what about using a simple error trap? ie. if it is unable to save the file, throw a warning message, save as another file name, etc.