SDK- Dynamic "Enable" and "Disable" of a field

[sinaei]

Hello Experts,

I have a requirement, we have created two custom fields via PDI in our serviceRequest BO. "Brand" and "Category"

the Enability of Brand depends on value of Category. if CAtegory is empty, then Brand should be Enable and user can insert a value, but if there is a value for Category, then Brandshould be Disable.

We need to check this logic when we open a ticket OR when we modifying a ticket.

I have tried two ways:
1) I have created a library and defined there the logic and in UI I have created a dedicated field with transformation. and bound the result of the library (That is True or False) with Enability of Brand!
It is working fine, but the problem is that It will word just when we open a ticket. I mean if we modify this ticket it can not call again the Library and check if conditions are set or no.

2) I've created a custom field that is Indicator and will save the result of check in Eevent-After-Modify and Event-AfterLoading.
So i UI I bound the Enabled behaviour to this field
Also here is the same, It just check the condition on Opening the Ticket, I mean for example if we open a ticket that the "Category" field is empty, then Brand is Enable, but if I modify the ticket and insert a "category", it will not set Brand Disable

can anyone help me how can I solve this issue?

Does anyone have any idea?

Regards
Sin