When a value changes in a control, the control that relies on that value needs to be requeried. You could use the after update event of the 1st control to requery the dependent control. You could also do it at the form level using requery, recalc or refresh methods, but that would affect the whole form and might cause issues. So try using the after update event of the 1st control.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.