CRM formula datecomp

CRM formula datecomp

Hi, we are currently using a formula in Zoho crm to calculate query response time.
It looks as follows :
Datecomp(${Marketplace - leads.First contact date & time},${Marketplace - leads.Creation time})
We want to make it so that the time only counts from Monday to Friday from 9am to 5pm, outside this range it is not to count. 
Someone can help?