How to catch Input to Access 2007 form before populating controls? Or assign different Inputs to different Controls?

Question

Heya guys,

Tough question here (for me at least);

Here's the sit: I have a form base application in Access 2007 (must). There are a few forms which have exactly two (2) text boxes that allow input.

Ideally, I'd like each of the text boxes to be mapped to different input devices, a Magnetic Swipe Card reader and a Barcode/Datamatrix reader.

1. Is there a way to map text boxes to different input devices?
2. Is there a way to catch the input to the form before it actually reaches the text box?

If 1 is impossible in Access, then 2 may be used to circumvent the issue by assigning the correct text box to write into by checking various properties of the input.

Further more, the 2nd question's resolve is needed cause with the swipe card, for example, I always get an input of 30 characters, out of which I only need 7 that begin with the 8th character - how would I do that?