Working with percentages in Adobe Acrobat 9 Pro

Question

So, I have a quick question. I am new to working with forms in acrobat, and am having a hard time figuring this part out. If anyone can help me, I would greatly appreciate it!
So I have a form that I've created in acrobat 9 pro. Below I have listed "individual 1:" and then "percentage allocation". The "percentage alloctions" are the different form fields for the percentages I've created. For each form field, I limited the values to not exceed 100%. I want individuals filling in this form to be able to fill in the percentages by each of the names without the TOTAL percentage value (of all three together) going over 100%. But...the trick is, I don't have a separate "Total" form field, there's no room for one. So is there a way to make it so the total of the three equals 100% without having a "total" form field?
individaul 1:  percentage allocation
Individual 2: percentage allocation1
Individual 3: percentage allocation2
Please let me know if this makes sense,

Answer 1

Try67,
Thank you for sending me that reference guide, that will help. This is extremely frustrating for me. Thank you for the field visible or hidden script...I did end up finding those yesterday, just didn't know how to incorporate them to become visible if the total number is less than 100.
I ended up creating another text field right next to the total, and called it "statement". I marked this field as "hidden" through the general properties option in the adobe acrobat dialog box. And , I set up default text to read, "Total value must not be less than 100%". All of this, I did through the properties dialog box.
Individual 1: 30
Individual 2: 20
Individual 3: 10
Total:  60%             "statement" text field is here.
I figured what I could do is add another "if statement" to the validation script I put in for the "Total" text field I already had (below)..don't know if that was a stupid thing to do or not, but didn't know how else to do it. And where it says getField, I added the "statement" text field (the one that is hidden), thinking it would just get that field, but it's not working, what did I do wrong?
var total = Number(getField("individual1").value) + Number(getField("individual2").value) + Number(getField("individual3").value);
if (total>100) {
    app.alert("The total of the beneficiary fields must equal 100%");
    event.rc = false;
if (total<100) {
this.getField("statement").display = display.visible;