Using a gps for marking property lines?

I want to buy gps but need to know if I can do the following - will a handheld unit allow me to mark property corners (A - B for ex.), then plot a straight line from A about 3/4 mile through the woods to B? If so would the unit alert me if I am off (or on) that imaginary line? I want to do this for a fairly accurate idea of my property line(s).