Task Status(System Defined fields) value How to reflect in Account Form Grid(Custom field)

Hello Experts,

I have a task grid on account form.I have used a custom field-option set for Activity Status with values Open Cancelled Completed.If a value changes in option set ,user is allowed to change it within the grid itself,save the changes and once the Task form is opened the activity status is updated  at Task Form also as i have made a WF for this .It is working fine.

But what if I want that if anybody changes status on Task form then the same status should be reflected in Grid.Currently the Task form has System field for Activity Status so i am not sure how to do this?

Thanks in advance!!

Please post your queries if the problem is not clear to you :)