Making a field dynamically mandatory?

Hi,

I have a task to make Location field mandatory if the importance is high in Appointment.

For this i enhanced BT126H_APPT/ApptDetails  in the context node Btactivityh  GET_P_ACT_LOCATION  i did the coding.It is working fine.

Now the problem is

1) Importance->high               Location->mandt          Fine.

2)Importance->low                 Location->Not mandt.   Here mandatory mark(*) is getting is removed but field is getting highlighted with red color.

I have attached screen shot

Can any body please tell me how can i handle this?

Thanks,

Hari.