Disable text fields on drop down selection

You can use this code as the custom validation script of your drop-down field, then:

var prefixes = ["Name", "Perc", "Credit Score"];
var selectedValue = Number(event.value);
for (var i=1; i<=4; i++) {
    for (var j in prefixes) {
        this.getField(prefixes+i).display = (selectedValue>=i) ? display.visible : display.hidden;
    }
}

Make sure to tick the option to commit the selected value immediately, under the Options tab of the drop-down's Properties.

Edit: Small mistake in code fixed