In my wells' form I have a dropdown...

[Kiyimbagrace]

In my ‘Wells’ Form I have a dropdown on ‘Well purpose’ field with the following entries: Injection, Appraisal, Observation, Production, Wildcat.

I have another dropdown on the ‘prospect’ field with several prospect names which are updated in a separate ‘prospect’ form.

I also have another dropdown on the ‘Discovery’ field with several discovery names which are updated in a separate ‘discovery’ form

I want to be able to LOCK the ‘Prospect’ field on condition that I have selected either: Appraisal, Injection, Observation, or Production from the dropdown on ‘Well purpose’.

The ‘Discovery’ field should remain UNLOCKED.

However, if I select Wildcat, the ‘Prospect’ field MUST Unlock automatically, and the ‘Discovery’ field gets Locked automatically.

I would like this to be the case even when I change the entries in those fields.

I thank you for taking your time to read this.

[zmbd]

You will need to use the after update event in the dropdown for the control for "Purpose"

What I would do, depending on how the control is setup, take the value from the "Purpose" control and then use a Select-Case construct to test for the correct values and then set the other two contol's enabled properties as needed.

In the design of the form, I would set the enabled property for "Prospect" and "Discovery" to default to "false" thus, on load they are locked by default forcing the user to make a selection in the "purpose" control before being able to do anything else with the other two controls.

Please make note that Bytes is neither a code writing nor homework service; however, we'll be more than happy to help you with any code that you currently have in the form.

[Rabbit]

You will also want to call the code in the on current event.

[zmbd]

Rabbit, as usual has a point there; however, this partially why I made the statement, "(...) depending on how the control is setup(...)" as I don't know if or how your form "Wells'" is bound to the underlying database.

[Kiyimbagrace]

Thank you both Rabbit and zmbd. kindly note that I am not a guru in writing code. The form "wells" is bound via foreign keys from the "wells" table to the other tables in the database.
I tried using this event procedure below on the 'on update' but when I change or remove values the lock/unlock does not reset:

Private Sub Combo157_AfterUpdate()
If IsNull(Me.Combo157.Value) Then
Me.Combo153.Locked = False
Else: Me.Combo153.Locked = True
End If
End Sub

This is where I am stuck.

[Rabbit]

That's because you haven't tested for any of the conditions you specified earlier.

[zmbd]

yes exactly,
I would suggest you look at the "select...c ase" construct as the code is much easier to write.
You will need to understand what value is being returned from the first dropdown (is it the primary key, the text, etc) and then test based upon that.
One way to determine this is to look at the properties and then the control source.... can be a pain, and may be what you'll end up having to do anyway.
Easier is to place a debug.print me.yourcontroln amehere.value in the after update event, run your form, then press <ctrl><g> to open the immedates window and see what is returned.

[Kiyimbagrace]

Dear ZMBD and Rabbit, Thanx for your time. Your help in this regard is much appreciated. I am still working on this ...glad to know you are helping.