private Sub IbmScreen_BeforeSendKeys ( 
   ByVal sender As Object, _
   ByRef keys As String, _
   ByVal row As Integer, _
   ByVal column As Integer _
) As Boolean

The value of parameter keys contains the keys that are about to be sent. In the event handler function you may change the keys before they are sent to the host. The event can also be canceled by setting the return value of the event handler function to false. The return value false is the default if your event handler does not explicitly set it. If you cancel the event, the keys will not be sent to the host. By setting the function return value to true, the event continues with the keys in the parameter keys, which could contain different keys set by the event handler. The row and column parameters contain the location on the screen where the keys were entered.

Reference

IbmScreen Object
IbmScreen Members