Can I simply 'read' a file that is in use?

I am trying to use a StreamReader to read a file, but it is always in use by another process so I get this error:

The process cannot access the file '\arfjwknasgmed17\C$\FLAG CONDITION\CP-ARFJN-FLAG.XLS' because it is being used by another process.

Is there a way I can read this without copying it? Or is that my only option?