Open an external file through a link in a report

[smtest]

hi,
I am trying to open an external file through a url.

'<a href="file://' || [test] || '\' || [DEPTID]|| '"target="_blank">View JV Attachment</a>'

i am using the above syntax. It works when i right click and save the target but when i click on it. It says "cannot find the file, please make sure the path or internet address is correct"
i am trying to access a text file on my machine.
please advice
thanks