onmouseup Property
Returns or sets a Variant that represents the value of the onmouseup attribute that is the name of the script to run when the onmouseup event fires.
expression.onmouseup
expression Required. An expression that returns one of the objects in the Applies To list.
Example
The following example sets the onmouseup attribute for the BODY element in the active document.
ActiveDocument.body.onmouseup = "script()"