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.