you should start using the motorola SDK (or MDK or how they call it).
The SDK has functions to control the scanner and to get an event when a barcode has been scanned. That will solve all your troubles finding out how to route data that is comming via the keyboard emulation of DataWedge.
If you still want to go with DataWedge you have to set Form.KeyPreview to True and setup the datawedge to use a preamble to distinguish barcode data from typed data. Then in KeyPress/KeyUp or/and KeyDown event of the form check the incoming data and place it in the scan data input where you need it.
But I strongly recommand to use the Motorola SDK.