Visualforce page not performing action - salesforce

Question

I'm very new to visualforce/salesforce, I'm a horrible beginner with this so please pardon my probably easy problem.
I'm creating a page to keep track of conference budgets. Basically the user enters how much was set as a budget in one field, in the next the put the actual cost, and then in the third field SF/VF should calculate the 2 numbers and display the difference. I set up the fields(correctly I believe as this was easy) and set up a page. Right now when you enter information into the fields and click save nothing happens.
This is all above my head and I'm trying to find the answers in literature but not having a lot of luck.
Here is the code:
<apex:page standardController="Conference__c" sidebar="true">
<apex:sectionHeader title="Conference Budget" subtitle="{!Conference__c.name}"/>
<apex:form >
<apex:pageBlock title="Conference Budget" id="thePageBlock" mode="edit">
<apex:pageBlockButtons >
<apex:commandButton value="Save" action="{!save}"/>
<apex:commandButton value="Cancel" action="{!cancel}"/>
</apex:pageBlockButtons>
<apex:actionRegion >
<apex:pageBlocksection title="Conference Budget">
<apex:panelGrid columns="4" width="400px" cellspacing="5px">
<apex:outputText value="Item" id="Item"/>
<apex:outputText value="Budgeted" id="Budgeted"/>
<apex:outputText value="Actual" id="Actual"/>
<apex:outputText value="Difference" id="Difference"/>
<apex:outputText value="Advertising" id="advertising"/>
<apex:inputField value="{!Conference__c.Advertising_b__c}"/>
<apex:inputField value="{!Conference__c.Advertising_a__c}"/>
<apex:inputField value="{!Conference__c.Advertising_d__c}"/>
<apex:outputText value="Totals" id="totals"/>
<apex:inputField value="{!Conference__c.Total_Cost_b__c}"/>
<apex:inputField value="{!Conference__c.Total_Cost_a__c}"/>
<apex:inputField value="{!Conference__c.Total_Cost_d__c}"/>
<apex:actionStatus startText="applying value..." id="status"/>
</apex:panelGrid>
</apex:pageBlocksection>
</apex:actionRegion>
</apex:pageBlock>
</apex:form>
</apex:page>

Answer 1

The main thing to realize is that Salesforce (unless you have some type of workflow set up) isn't going to calculate those fields automatically. In addition, simply saving a record inside of an action region won't save the record, reload it, and display the page again. Saving, as far as I know, redirects the user to the record detail page.
For this simple calculation, if you want ti calculated prior to saving the record, I would just use some simple javascript:
<apex:page standardController="Conference__c" sidebar="true">
<!-- I use JQUERY because Salesforce IDs are very difficult to utilize in standard JS -->
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js"></script>
<script type="text/javascript">
var $j = jQuery.noConflict(); // SFDC uses $ so we need to assign jQuery to something else
function recalcAd() {
try{
var budget = parseFloat( $j("input[id$='ad-b']").val() );
var actual = parseFloat( $j("input[id$='ad-a']").val() );
$j("input[id$='ad-d']").val(budget - actual);
} catch (e) {
$j("input[id$='ad-d']").val("");
}
}
function recalcTot() {
try{
var budget = parseFloat( $j("input[id$='tot-b']").val() );
var actual = parseFloat( $j("input[id$='tot-a']").val() );
$j("input[id$='tot-d']").val(budget - actual);
} catch (e) {
$j("input[id$='tot-d']").val("");
}
}
</script>
<apex:sectionHeader title="Conference Budget" subtitle="{!Conference__c.name}"/>
<apex:form >
<apex:pageBlock title="Conference Budget" id="thePageBlock" mode="edit">
<apex:pageBlockButtons >
<apex:commandButton value="Save" action="{!save}"/>
<apex:commandButton value="Cancel" action="{!cancel}"/>
</apex:pageBlockButtons>
<apex:pageBlocksection title="Conference Budget">
<apex:panelGrid columns="4" width="400px" cellspacing="5px">
<apex:outputText value="Item" id="Item"/>
<apex:outputText value="Budgeted" id="Budgeted"/>
<apex:outputText value="Actual" id="Actual"/>
<apex:outputText value="Difference" id="Difference"/>
<apex:outputText value="Advertising" id="advertising"/>
<apex:inputField id="ad-b" value="{!Conference__c.Advertising_b__c}" onChange="recalcAd(); return true;"/>
<apex:inputField id="ad-a" value="{!Conference__c.Advertising_a__c}" onChange="recalcAd(); return true;"/>
<apex:inputField id="ad-d" value="{!Conference__c.Advertising_d__c}"/>
<apex:outputText value="Totals" id="totals"/>
<apex:inputField id="tot-b" value="{!Conference__c.Total_Cost_b__c}" onChange="recalcTot(); return true;"/>
<apex:inputField id="tot-a" value="{!Conference__c.Total_Cost_a__c}" onChange="recalcTot(); return true;"/>
<apex:inputField id="tot-d" value="{!Conference__c.Total_Cost_d__c}"/>
</apex:panelGrid>
</apex:pageBlocksection>
</apex:pageBlock>
</apex:form>
</apex:page>
In the code I've added some some script that will recalculate the totals as well as removed the action region which seemed unnecessary. I wasn't able to test it (since I don't have that object set up in an account of mine) but I think it should work for you.