cant create an instance of excel.application

hallo, everyone,

we have a Desktop-App (vb.net), and need open Excel from program, and we just used 

xlsWorkbook = CType(System.Runtime.InteropServices.Marshal.BindToMoniker(filePath), Excel.Workbook)

xlsApp = CType(xlsWorkbook.Parent, Excel.Application)

and it works fine except by one user,

and we tried 

xlsApp = New Excel.Application     or 

xlsApp = CType(CreateObject("Excel.Application"), Excel.Application) 

and it cant work with his computer, by other users are ok.

i think its nothing to do with our code, just one com-component in his computer is missing, such like interop.excel.dll or sth else.

anyone know this? can anyone help?

thanks a lot!