Fill field by default in mobile application

Hello,

We need to configure the Event field in the Lead object to be automatically prefilled for users in the mobile application. Since different managers are assigned to different events, the value should be dynamically calculated based on the specific user and prepopulated in the field.

Please note that this functionality should only apply to the mobile app and not the web version.

What would be the best approach to achieve this?

Thank you!
Vladimir