DinØ,
How automated should this be? Is selecting the DXF an option or should it select automatically? You want two routines, one that explodes, one that doesn't, right? Do you want the viewport to fit only, or kinda fit to scale? Should it all be one button, or break it up? For instance, if the may need to manipulate the VP manually, you might be best off having a button to lock the VP after it is set correctly.