I got my selection working. Now I need to assign the white fill to it. Here what I have so far:
var doc = app.activeDocument;
var oldUnits = preferences.rulerUnits;
preferences.rulerUnits = Units.PIXELS;
var mySelection = [[100,580], [100,350], [600,350], [600,580]];
doc.selection.select(mySelection);
doc.mySelection.fill ("White");
Thank you.