iam doing windows app. in WPF
in Datagrid shows customer details,
now i need to add one column for timer,
ie, Each row having start button, while press the start button that current row timer starts now and hide the start button and show stop button.
so finally press the stop button, we calculate the logged in duration....

Table Fields

cust.ID Name start time End time start/stop

we click start button means set current time to start time and timer starts end time time column.
we click stop button means stop the time and calculate duration and set end time.
this process happen in each row...

tell me the soln, its very urgent