The mouse up action is executed when after the mouse button is released.
For a button use click events, if you are using radio buttons, also use the click event.
Straight from ES2 help
mouseUp event
Description
Initiates when a form filler releases the mouse button at the same time that the pointer is within a field.
Note: When a
mouseUp event occurs for a text or numeric field, calculations or scripts run immediately. However, the value of the field does not change in response to calculations and scripts until the field loses focus.