Visio 2003 Dragging master to control - data type?

[Peter Collins]

im trying to get the data type that a control receives when a master is drag dropped from a visio stencil to an external control. the following gets inside the if, but the application jumps back to the gui at the type cast (im guessing an exception should be thrown, but it seems no exceptions are ever thrown by the control, it always just jumps back to gui (as if u selected ignore/continue)

If e.Data.GetDataPresent("Visio 11.0 Masters") Then
Dim master As Visio.Master = CType(e.Data.GetData("Visio 11.0 Masters"), Visio.Master)

End If