Delay Days Calculation

Delay Days Calculation

I Have create a planned day(Formula Type) to Calculate base on start date and End date , i have also created a delay day(Formula Type) to calculate base on End Date and Completion Date 

I have problem that I have issue that I am getting the value include weekend and holidays also in both Field but I need only days value of my working Hours (mon-sat) but doesn't count sunday's in it.

Planned Day function : DATETIME_DIFF({END DATE},{START DATE},'DAYS')
Delay Date Function : DATETIME_DIFF({COMPLETION DATE},{END DATE},'DAYS')

Anyone Can Solve This