can't using direct alias to input data into text field

Hi all,



I want to fill data into text field. As normally, I use alias["Keys"] to input data



It like that 


  objPage = Aliases["iexplore"]["pBroadcastCalendarReport"];  

  objPage["txtBroadcastYear"]="2010"



But the data isn't filled on textfield. When I debug and objPage["txtBroadcastYear"]["Exists"] is False although it's shown on webpage



And I must a temporary variable to do that and it's work OK

objPage = Aliases["iexplore"]["pBroadcastCalendarReport"];  

var textbox=  objPage["txtBroadcastYear"]

textbox["Keys"]="2010"



Could anybody help me to explain what's different between two above ways?



Thanks so much