This doesn't seem to be different from your other post on Business Day Metric. Same logic should work here also. You can have a simple flag called BusinessDay in your Date table. The flag will have 2 values, 1 for BusinessDay and 0 For NonBusinessDay. NonBusinessDay will be set for Holidays and Sundays. After this is set, it is a count of date filtered on BusinessDay flag set to 1.
The BusinessDay flag should satisfy both your posts on the date metrics.