disable the default Enter/Return key behavior in a datagridview

You can try something like this in the gridview key down event

Private Sub DataGridView1_Keydown (...) Handles DataGridView1.KeyDown
   If e.KeyCode = Keys.Enter Then
       ' Your code here
       e.SuppressKeyPress = True
  End If 
End Sub

Another option would be to create a custom grid view control

DataGridView.ProcessDataGridViewKey Method

You can just use keyPress event:

 private void dataGridView1_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                //You're Code
            }
            e.Handled = true;
            return;
        }