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.
You can use this event to perform actions as a direct response to a form filler clicking a button, or selecting a radio button or check box on a form. For example, you can use the mouseUp event for a check box to hide and show a field on the form. This event is conceptually similar to the click event and has a similar purpose.
See also 

mouseUp event