Programmatically Set The Object Type For A DirectCast Command?

I'm helping a colleague develop a "catch all" type error handler for some controls his application. What he wants to do is pass the object that has the error, and the type of that object, such a TextBox or ComboBox, and then call the DirectCast method within his handler to properly address the Text attribute within it. In general, the method is looking like this:

Protected Sub SpecialErrorHandler(ByVal TargetControl As Object, ByVal ControlType As String)
MessageBox.Show("Bad Juice: " & DirectCast(TargetControl, ControlType(ObjType)).Text)
End Sub

So far any attempts to do a type conversion within the DirectCast method (since it is expecting an object in the general signature) or to even pass in the a Type object properly set is not working.

Any ideas here, or is this one of those "Casting doesn't work that way." type scenarios?