I used the code that F.Bowman came up with and was able to get it to work on my dataGrid just fine.  However, the dataGrid in my form is only part of the form.  I'd like to be able to use this on things like text inputs, combo boxes, and my dataGrid all in the same form.  If I change the code posted above to attach the event handler to and dispatch the event from the stage, I can use the Enter key to move from text box to text box to combo box to whatever just fine, but then when it focuses on the dataGrid, the dataGrid no longer uses Enter in place of Tab, nor does it default back to moving down one row either.  Here is my current code:

public function applicationCompleteHandler():void {
  stage.addEventListener(KeyboardEvent.KEY_DOWN, keyHandlerStage, true, -10000);
}

private function keyHandlerStage(e:KeyboardEvent):void {
  if(e.keyCode == 13) {
    e.stopImmediatePropagation();
    stage.dispatchEvent(new FocusEvent("keyFocusChange",true,true,null,false,9));
  }
}

I tried setting one event listener on the stage and then one on the DataGrid, with different priorities for each, and got nothing.  Also, if I use a trace to display the keyCode of the button pressed in the stage's event Handler, it displays "13", which is normal.  But, if I trace the keyCode of the dataGrid's event handler, it doesn't display "13" when the Enter key is pressed, but it will display the keyCodes of every other key I press in the dataGrid.

Any idea what I'm doing wrong?

Okay, well, I'm closer.   With this code, I can use the Enter key just like the tab key both in  and out of the DataGrids, except when I hit a custom itemEditor in the  dataGrid.  Here's what I have now:

public function applicationCompleteHandler():void {
  stage.addEventListener(KeyboardEvent.KEY_DOWN, keyHandlerStage, true, -10000);
}

private function keyHandlerStage(e:KeyboardEvent):void {
  if(e.keyCode == 13) {
    var focused:Object = e.target.parent.parent.parent;
    var check:Boolean = focused is DataEntryDataGrid;
    if(check == false) {
      e.stopImmediatePropagation();
      stage.dispatchEvent(new FocusEvent("keyFocusChange",true,true,null,false,9));
    } else {
      focused.dispatchEvent(new FocusEvent("keyFocusChange",true,true,null,false,9));
    }
  }
}

DataEntryDataGrid on line 8 is a subclass of mx:DataGrid.  If I trace e.target while an editable cell of the datagrid is selected, I get this:

HerringSurveySpawn2.ApplicationSkin2._ApplicationSkin_Group1.contentGroup.Group6.crewGrid.ListBaseContentHolder105.HerringSurveySpawn2InnerClass0_364.UITextField366

In the above line, "crewGrid" is the id of the dataGrid that is focused on when the Enter key is pressed. This is what led me to the e.target.parent.parent.parent idea in the code block above.  But, when I hit a custom itemEditor, like a comboBox or something, the whole thing breaks.  There are three levels after "crewGrid" in a regular textInput-style cell, but only two levels after "crewGrid" when tracing from a comboBox itemEditor cell.  What I'd really like is to be able to check if e.target is a child of a dataGrid at any level, but I'm not sure how to accomplish that.  I'm sure that if I could get that figured out, it would work like a charm.

Tried that and it didn't work.  It broke the Enter key for the regular textInputs inside the dataGrid as well.  When I traced the output of focusManager.getFocus() while a datagrid cell was selected, I got:

HerringSurveySpawn2.ApplicationSkin2._ApplicationSkin_Group1.contentGr oup.Group6.crewGrid.ListBaseContentHolder105.HerringSurveySpawn2InnerC lass0_364

When what I think I was looking for was simply:

HerringSurveySpawn2.ApplicationSkin2._ApplicationSkin_Group1.contentGr oup.Group6.crewGrid

The form has two different dataGrids in it, both used for data entry.  How would a "parent walk" work?

That's perfect.  It works like a Swiss clock now.  Here's the final code, for anyone else who might find this thread and need it:

// Call this function in your application's "applicationComplete" event
public function applicationCompleteHandler():void {
  stage.addEventListener(KeyboardEvent.KEY_DOWN, keyHandlerStage, true, -10000);
}

private function keyHandlerStage(e:KeyboardEvent):void {
  if(e.keyCode == 13) {
    var focused:Object;
    var check:Boolean = e.target is DataEntryDataGrid;
    if (!check)
    {
      var o:DisplayObjectContainer = e.target.parent
      while (o != this.stage)
      {
        if (o is DataEntryDataGrid)
        {
          check = true;
          focused = o;
          break;
        }
        o = o.parent;
      }
    }
    if(check == false) {
      e.stopImmediatePropagation();
      stage.dispatchEvent(new FocusEvent("keyFocusChange",true,true,null,false,9));
    } else {
      focused.dispatchEvent(new FocusEvent("keyFocusChange",true,true,null,false,9));
    }
  }
}

Thanks, Flex!