I am familiar with solutions from here https://help.zoho.com/portal/en/community/topic/calculate-number-of-business-days-weekdays?reply=true

But I don't understand how to use it.

I have formula field named "Day" with this formula: 

((zoho.currentdate - Start_Date)  /  (1000  *  60  *  60  *  24))

"Start_Date" is data field.

I want in output to exclude weekend days (Saturday and Sunday). In other words I want formula only to calculate business days.

I am happy to pay consultant for help.