How to set a Priority field value onLoad only

[ss123]

Hi!

We have a requirement where we need to set the Priority to field to --None-- (this is from the Dropdown with None) when a case form is newly created and HR Service = "HRServ1" (sample only)

I achieved this using UI Policy but the problem is, when we changed the Priority value to other options then click  Save or Update button, it goes back to Priority value "--None--"

Thanks in advance

[Harish KM]

I tested in my PDI my BR works fine during case creation and I can change priority to other options.

[ss123]

Thank you harish. validated that this Br is working to other fields but not to Priority field. Maybe there's other configuration on the field.