I'm not sure if this is exactly what you need but the Call Executable step can be used to issue a DOS 'Tasklist' command. If Excel is open, the STD Out should have 'EXCEL.EXE' listed if Excel is running. Is this what you mean by 'in use?'.
Im im looking for is to find out if i have write permissions on a specific workbook.
If i dont have write permissions and the file is opened by another user i would like you know who the user is and worn my user.
What you need to do is open LabWindows/CVI and create an ActiveX controller by going to Tools>Create ActiveX Controller.
You will be able to build a library for the Excel ActiveX Server: called Microsoft Excel Object Library.
From there you can select which methods and properties will be placed into a C wrapper.
After the previous operation is complete you will find a .obj file in your project folder.
At this point you can use the functions that were created in CVI or load them into TestStand.
Too load them into TestStand open up a CVI Action step and select the created object library file as the code module. From there the function list will populate with all the functions available in the library.
You will need to look at the available ActiveX Automation Server functions available to control Excel and find the ones you need for your specific application.