Returns the value of a given parameter specified by an index. The index value is zero-based, so an index of zero returns the second parameter.
string uChoice(index, values, ...)
uChoice(0, "A", "B") // returns "A"
uChoice(1, "A", "B") // returns "B"
uChoice(2, "n.a.", "Jan", "Feb", "Mar") //returns "Feb"
uChoice(IN.Color, "n.a.", "Red", "Blue", "Green")