Call __dopostback from modal dialog

Question

I have a custom form in my SharePoint 2010 site. There a couple of things to note here:

1. My custom form is in a SharePoint modal dialog

2. I have a 2nd modal dialog that prompts the user if they "really" want to save a duplicate record

In the first dialog, a user will type in a bunch of information. If they type a duplicate record, in the 2nd modal dialog, they will be asked if they want to save a duplicate record. If they answer yes, I need to go back to the first modal dialog, do a postback and save the information they entered. The trouble I'm having is that I cannot get the form to postback to the server side code to actually save the record. Can someone help? Below is my code, but if someone wants to show me a different way, I am open to that.

Markup for the dialog modal.

<div id="hiddenDuplicateErrorMessage" style="display: none;">
<p style=" padding: 5px; font-size: 11pt;">You are attempting to create an award    
that matches an existing award in the Awards Tracking System.
 If this is a unique award submission, click 'Submit' to continue with the award   
submission, or 'Cancel' to return to your award form to revise 
 your submission.</p>
<p style="width: 100%; text-align: right;">
    <button id="btnSubmitDuplicateAward" 
onclick="javascript:doPostBack('<%=btnSubmitFormConfirmed.ClientID %>','')" 
type="button">Submit</button>
    <button id="btnCancelDuplicateAward" type="button">Cancel</button>
</p>
</div>
<div style="display:none;"><asp:Button ID="btnSubmitFormConfirmed"    
OnClick="btnSubmitFormConfirmed_Click" runat="server" /></div>

<input type="hidden" name ="__EVENTTARGET" value ="" />
<input type="hidden" name ="__EVENTARGUMENT" value ="" />

Javascript Code for the confirmation dialog

function doPostBack(eventTarget, eventArgument) {
document.aspnetForm.__EVENTTARGET.value = eventTarget;
document.aspnetForm.__EVENTARGUMENT.value = eventArgument;
document.aspnetForm.submit();
}

Code Behind that checks to see if a duplicate and creates the prompt to confirm saving a duplicate.

if (duplicateAward)
ClientScript.RegisterStartupScript(this.GetType(), "ShowDelayedErrorMessage",   
"ExecuteOrDelayUntilScriptLoaded(function () { var myControl =   
$('#hiddenDuplicateErrorMessage').html(); openDialog(null, 'Error Creating Award',  
myControl); }, 'sp.ui.dialog.js');", true);