Different text when selectable

I was just wondering how to display an option with different text depending on whether it’s selectable or not. I mean that the selectable_if would tell you why you couldn’t select something. Ie. If you’re not strong enough the greyed out option would say that, but if you were strong enough it would show up as “lift the weights” or something like that. I’m pretty sure I saw that in Study in Steampunk, but I haven’t been able to find it in the help.

*if (money > 500)
    *set money_desc "Buy ..."
    *goto choice
    *set money_desc "If only I had enough money to buy..."
    *goto choice

*label choice
    *selectable_if (money > 500) #${money_desc}