Automatic Mandation of a field value

Hi all, My Requirement is as below.

Say I have two fields A and B in my editor presentation.

When I select a value say X for the field A using the drop down(Enumeration), the field B should be automatically mandated to move to the next phase(When we save).

But, when I select a value other than X for the same field A, the field B should not be mandated.



Could you please help me in achieving this scenario.


Thank you,

Kishore Royal