How to do the checking if a datagrid being changed or not ??

Question

I have put a DataGrid onto form1, and that datagrid has 2 fields - CustomerCode and CustmerName .. User can actually edit the data on the datagrid itself ... My problem is : When user are goin to close the form, the system will check if there's anything changes made in the datagrid .. if No, the form will close .. otherwise a messagebox will pop up asking whether they want to save the changes .. So the problem is how am i going to make the checking whether the data is being changed or not ?? For your info, the datasource for that datagrid is linked to datatableCustomer ... Hope someone can help thanks in advance..