Workaround: use custom editor element private void radGridView1_EditorRequired(object sender, EditorRequiredEventArgs e) { if (e.EditorType == typeof(RadMultiColumnComboBoxElement)) { e.EditorType = typeof(MyRadMultiColumnComboBoxElement); } } public class MyRadMultiColumnComboBoxElement : RadMultiColumnComboBoxElement { protected override Type ThemeEffectiveType { get { return typeof(RadMultiColumnComboBoxElement); } } protected override void ProcessKeyDown(object sender, KeyEventArgs e) { base.ProcessKeyDown(sender, e); FieldInfo fi = this.GetType().BaseType.BaseType.GetField("oldTextValue", BindingFlags.Instance | BindingFlags.NonPublic); fi.SetValue(this, this.textBox.Text.Substring(0, this.textBox.SelectionStart)); } }