How to import a data sheet from Quality Center ?

In my script, i was picking up the data from an external sheet located on my desktop which i was importing using
DataTable.ImportSheet ("C:desktopabc.xls", "", "")
The above is step is working fine. Now, i am supposed to upload my script in QC. For which i uploaded the excel sheet as an attachment in QC & updated the path of the excel sheet in my script.
But, while running it is throwing an error as "Run Error: File not Found at the specified path"

Has anyone encountered this problem? Am I missing something obvious? Does anyone have a solution?

Thanks in advance.