dax formula

Description

i want you to write a dax formula

i have many tasks and every task assigned to employee 

this emplyee is working and we follow his progress related to what time he start and stop

i want to calculate the time which worked on to find how many hours he worked. 

i attached my sheet .

the table name is ( update) 

starting work ony if the status is (check in) , otherwise meaning he stoped

want to calculate the time spent , i think should create column