Tab in DataGrid (Windows)

Hi, I have a little problem

I have a datagrid with 4 columns:

| 1 | 2 | 3 | 4 |
| Value | VatCode | VatVal | NomCode |

I am trappping the cellchange event of the DataGrid and if the Value of VatCode colums are being left then the VatVal is calculated. The problem I have is that when I tab from NomCode (in row 0) to Value (in row 1) the cursor moves back to row 0. It is the line below that moves me back:

DGInvoice.Item(intCurrentRow, 2) = CDbl(.Item(intCurrentRow, 0)) * (dblGetVatRate / 100)

I know that the row number is changing at this point because I have put a msgbox above and below it to test what row I am on.

Does the allocation of a cell move you to that row or am I just going CRAZZYYYYYY??????

Thanks for your time