I have a custom component based on the TitleWindow component and I have
declared a bindable public variable in that custom component's script tag. In
my app If the user clicks a button, flash will open the title window using the
PopUpManager. After it is opened, I want to pass in some data. I have tried
doing this a number of different ways, but have failed. Can someone help me?
Thank you in advance!

import mx.core.Application;

titleWindowClickHandler(event:MouseEvent):void{
titleWindowVar = Application.application.mainAppVar;
}

Thank you for responding. I don't quite get the third line of your code. This
is the function where I call the PopUp:

public function editQuote():void {
//Fill in fields of SingleRecordDetail component
//currentStudent = quoteGrid.selectedItem;
//Open the Quote_SingleRecord pop up
var editQuoteWindow:TitleWindow = TitleWindow(PopUpManager.createPopUp(this,
quoteSingleRecordDetail, true));
PopUpManager.centerPopUp(editQuoteWindow);
//Set the value of the bindable variable that will determine the title of the
Quote_SingleRecordDetail panel
var selectedStudentName:String = quoteGrid.selectedItem.lastname + ", " +
quoteGrid.selectedItem.firstname;
editQuoteWindow.title = "Editing Quote for: " + selectedStudentName;
currentStudentAsProperty = quoteGrid.selectedItem;
}

I solved my problem. I changed the variable type to the name of my custom
component. From the code I pasted above, this is the only edit:

var editQuoteWindow:quoteSingleRecordDetail =
quoteSingleRecordDetail(PopUpManager.createPopUp(t his, quoteSingleRecordDetail,
true));