Combo box value requirement for query row source

[jimmyac23]

I am working in MS Access 2007 and have a form with combo boxes whose row sources are pulled from a query. How do I make sure that these values are required?




For example, I have other combo boxes whose row sources are from a table, and with those table values having a required property, a message appears every time I click my command button to insert a new record stating that the command box value must be entered. I want to replicate this result for the command boxes whose row sources are from a query, but do not know how to do so.


I have tried several different methods:
*Creating a validation rule in the property sheet, but I need to make sure that the the combo boxe's value cannot be null or cannot be an empty string aka "".
*Using VBA to set the Validation Property, but I am still able to add the record and don't get a warning message.
*Using VBA to create a MsgBox if the combo box is null when the command button is clicked, but this doesn't seem to be successful.


Thank you and have a great weekend!

[orange]

Please show some related code.

[jimmyac23]

Option Compare Database


Function SetValidation(stringtxt As String)
    Set ContactPosition.ValidationRule = stringtxt
End Function






Private Sub ContactType_AfterUpdate()
    ContactPosition.Requery
    ContactPosition.Value = ""
End Sub


Private Sub Region_AfterUpdate()
    Borough.Requery
    Borough.Value = ""
    Neighborhood.Value = ""
End Sub


Private Sub Borough_AfterUpdate()
    Neighborhood.Requery
    Neighborhood.Value = ""
End Sub




Private Sub SubmitCommand_Click()
    If IsNull(ContactPosition) Then
    MsgBox ("Test")
    End If
End Sub