CustomAction Event
Occurs when a custom action of an Outlook item executes. The Action object and the newly-created item resulting from the custom action are passed to the event.
Sub object_CustomAction(ByVal Action As Object, ByVal Response As Object, Cancel As Boolean)
object An expression that evaluates to one of the objects in the Applies To list. In VBScript, use the word Item.
Action Required. The Action object.
Response Required. The newly-created item resulting from the custom action.
Cancel Optional (not used in VBScript). False when the event occurs. If the event procedure sets this argument to True, the custom action is not completed.
Remarks
In VBScript, if you set the return value of this function to False, the custom action operation is not completed.
Example
This example uses the CustomAction event to set a property on the response item.
Function Item_CustomAction(ByVal myAction, ByVal myResponse)
Select Case myAction.Name
Case "Action1"
myResponse.Subject = "Changed by VB Script"
Case Else
End Select
End Function