Yes!
Try:
DataGridTextBoxColumn aCol4 = new DataGridTextBoxColumn();
aCol4.MappingName = "Percentage";
aCol4.HeaderText = "Percent";
aCol4.Width = 50;
aCol4.Alignment = HorizontalAlignment.Right;
aCol4.NullText = "0";
aCol4.TextBox.Enabled = true;
aCol4.Format = "{0:P}%";