Auto assign booking confidence % based on opportunity stage

As an individual contributor (role: sales) using salesforce to manage pipeline/opportunities. I'm wondering if i can create a rule to assign a predefined booking confidence % by opportunity stage? (e.g. when i move an opportunity to the "proposal" stage, i want the booking confidence % to auto update to "50%".

I've got a fairly unhelpful internal staff to help me with this request so wondering if i can do this with the permissions i have?