clear a field if condition met

[JSDART!!]

HI
I am working with a mesage box with yes and no that is triggered on the lost focus event after the discharge date is entered
if yes the users is thanked and approved to go on to the next step.
If no the user is prompted to complete the task and retun to enter the discharge date.
I would also like to delete the dischage date forcing the user to complete the task before the discharge date can be recorded any Ideas.
I was looking at using a macro with senkeys {del} but not successful thanks

 

[JSDART!!]

never mind I just switched it to on focus and it works