Force Update of Expected Revenue through custom function

Force Update of Expected Revenue through custom function

I have created a custom function that when coupled with workflow rules will take the amount of a quote that has been marked as "closed won" and update the amount of the related potential to match. The workflow set also updates the potential stage to "Win" and the closing date as today's date. What I have noticed is that even though the amount has changed and the probability has been increased to 100%, it uses the old Amount for the calculation instead of the new one. 

Is there a way to have it force another update of this calculation so the expected revenue is accurate? This will keep our forecasts accurate as well.