ms/access dynamic source for dropdown control

On my app o have a 4 level table subtable set for a location: Region / Sector / Section / Base. I need to have the user selecting first the [Region] then, only the [Sector] for the selected [Region] should show on the dropdown [Sector] control, then only the [Section] set for the the selected [Region].[Sector] should show on the dropdown.
All the controls have specific proper names, e.g.  [frmfld_Region] for the dropdown control related to Region.
My question is: how do I do it? How do I ensure that the dropdown list is properly managed? (a simple tree as in datasheet view would do ... but I can't simple use it as I loose the "control" management.
João serras-pereiraAsked:
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Fabrice LambertConsultingCommented:

you can use the BeforeUpdate event, to refresh or update the next dropdown lists.

This can be as simple as setting the rowSource property, to calling whatever function used to populate the dropdowns.
João serras-pereiraAuthor Commented:
Yeap... I was hoping that someone had the actual solution. The rowSource property is a query, as usual. But the query should be dependent on the values of higher level tables and this is precisely what I don't know how to....
Fabrice LambertConsultingCommented:
Most of the time, selecting something in a dropdown apply filter in the others.

So it is just a matter of writing the "where clause".
Without knowledge on how your controls are set up, I can only make some guess.

Let's say the rowSource for your Region control is something like:
Select Name
From Region;

And nothing in the rowSource of your Sector control.

On the beforeUpdateEvent, you should call:
Public Sub Region_BeforeUpdate(Cancel As Boolean)
    Sector.RowSource = "SELECT Sector.Name " & _
    "FROM Region INNER JOIN " & _
    "Sector ON Region.ID = Sector.ID" & _
    "WHERE Region.Name = '" & Region.value & ';"
End Sub

Open in new window

Hope you get the idea.

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João serras-pereiraAuthor Commented:
thanks!!! great HELP!
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