The Column property of a combobox or listbox lets you read the value of
columns that are not the Bound Column. However, you cannot read that
property directly in a query -- instead, you need to use a VBA function that
reads and returns it to your query.
Create the following function in a regular module:
Public Function ReadComboListBoxColumn( _
strFormName As String, strControlName As String, _
intColumnNumber As Integer) As Variant
' NOTE: intColumnNumber is a "zero-based" number, meaning that you
' must provide 0 to read the first column, 1 to read the second
' column, etc.
ReadComboListBoxColumn = _
Forms(strFormName).Controls(strControlName).Column(intColumnNumber)
End Function
Then use this function in your query:
SELECT Field1, Field2
FROM TableName
WHERE Field2 = ReadComboListBoxColumn("FormName", "ComboboxName", 1)