How to calculate time difference excluding weekends (saturday and

I have an Oracle table that has 2 Date fields..i.e. the data type -
DATE

Field 1:  START_DATE sample value  "2008-04-04 12:00:00";
Field 2:  END_DATE  sample value  "2008-04-07 05:46:07";

If I subtract one date from another, I can get the time difference.

Round((END_DATE - START_DATE), 4) AS TOTAL_DAYS

The above results in 3.7404

Between 2008-04-04 and 2008-04-07, there is Saturday and Sunday which
are 2008-04-05 and 2008-04-06.
I would like them to be excluded.

Hence, the resultant that I'm looking for should be 1.7404  -- not
3.7404

Is there a simple way to get the desired solution?

Thanks,
Deepak