//C#
CurrencyManager cm = (CurrencyManager)this.BindingContext[this.gridDataBoundGrid1.DataSource, this.gridDataBoundGrid1.DataMember];
((DataView)cm.List).AllowNew = false;
'VB
Dim cm As CurrencyManager = Me.BindingContext(Me.GridDataBoundGrid1.DataSource, Me.GridDataBoundGrid1.DataMember)
CType(cm.List, DataView).AllowNew = False