I don't think you can do that. As far as I know the only options for scale display are, decimal, fraction, and ratio.
Decimal = 0.250
Fractional = 1/4
Ratio = 1:4
I have never been able to find a way to use an Architectural scale like 1/4" = 1'. Maybe someone can prove me wrong, but you may be stuck entering it manually, if you want that.