finding date different between two collumn except saturday and sunday

Dear All,

i have two column of call logged date and closed date as the format of general ( actual data format is dd/mm/yy -hh:mm)

unable to change the format general to date format.

i need to find out the different hours between two days except saturday and sunday... ( 1 day working hours is 8:30 am to 6pm).

finally i need date different from two cells ( it would be helpful if you finding hours different)...

See the attached file