Working Days of Monday to Friday and working hours of 9am to 5:15 pm in duration formula

[lucyk]

Hi All,

how would I amend the formula below to include Working Days of Monday to Friday and working hours of 9am to 5:15 pm in the out put? 

INT(DATETIME_DIFF(NOW(), {Credit decision date}, 'hours')/24)&" Days "&MOD(DATETIME_DIFF(NOW(), {Credit decision date}, 'hours'), 24)&" Hours "&MOD(DATETIME_DIFF(NOW(), {Credit decision date}, 'minutes'), 60)&" Minutes"