Clear selected value from combo box

hey guys,

I am using SBO 2005 and I cannot seem to get the selected value to clear from the combo box. I used this code in 2004 and it worked:fine

this.itemDetailForm.DataSources.UserDataSources.Item("shipList").ValueEx = "";

But it throws an exception when I try it in 2004 and when I look in the XML my shipList is not part of the userdata sources.

How do I clear this value in 2005?