>Hi Dragan
>
>The question is for each field the valid values
>can be actual value (know to the user) or null (for value not known to the user) in the sql field.
>
>e.g. if we have a field called salary then the valid
>values can be Zero to some figure. But if the user
>does not have the information for that field then
>the value should be null.
>
>Please note that in above example even Zero
>is a valid value. Hence Zero and null value
>have there own meaning.
>
>Zero salary can be valid for a director of a company.
>Null value can be valid for a person for whom we don't have any information.
>
>Question here is how should be our data entry screen.

For numeric values you would get a zero whenever a textbox is visited by the user. You could perhaps add a checkbox or a button next to it, which, when clicked, would put a .null. into the controlsource of the textbox. Or, if possible, you could teach your users to press ctrl+0 (zero on main keyboard, not the numeric pad) when they want a null.