Sort field in maintenance order

Hello;

I want to make sort field in maintenance order as a mandatory field. But if I make it as a mandatory field, system still allows me to save the order as long as I have not clicked 'Location' tab. So there is no positive control over this field. May I know, how do I achieve this? I have even tried to put order type as the influencing field but it does not help.

Points assured.

Regards

Hemant