In Adobe Acrobat XI Pro, how do I validate a form field so that it's numerical value is less than or

Question

I have one numerical field named "B," and I need to validate it so that it is less than or equal to the value of another field named "A." I can't figure out how to do that!

Answer 1

OK, so the custom calculate script for field B could be something like:
(function () {
    // Get field values as strings
    var sA = getField("A").valueAsString;
    var sC = getField("C").valueAsString;
    var sD = getField("D").valueAsString;
    // Only perform the calculation if all fields are filled
    if (sA && sC && sD) {
        var sum = +sC + sD;
        event.value = sum;
        // Alert the user if the sum is more than A
        if (sum > +sA) {
            app.alert("Error message goes here");
    } else {
        // Blank this field if all fields are not filled in
        event.value = "";
Instead of (or in addition to) an app.alert popup, you could place this message in a read-only form field, and clear it if there is no error condition.