Access - VBA Sub not called [closed]

I am required to provide a way for users to choose which column they want to display from a table. The user has a combo box of column names in a form which they can select one of and then hit a button which opens a report. I wrote some code which creates an SQL query based on the user's input, but it's not being called. I've tried inserting MsgBox statements, asserts, etc., but it never gets called. If I use a macro instead, that will be run, but not this sub...

Private Sub Report_Open(Cancel As Integer)
    Dim field As String
    Dim sqlQuery As String
    Dim ctl As Control
    ctl = "Forms![RuleGroupForm]![selectRuleFieldCombo]"

    field = "rules.[" & ctl & "]"

    ' E.g. if the field was "Source File", the final query should look like this:
    'SELECT overview.ID, relationship.rulesID, rules.[Source File], overview.[Rule Group], rules.RulegroupID
    'FROM (overview INNER JOIN relationship ON overview.id=relationship.id)
    'INNER JOIN rules ON relationship.rulesID=rules.ID
    'WHERE rules.[Source File] IS NOT NULL;

    sqlQuery = "SELECT overview.ID, relationship.rulesID, " & field
    sqlQuery = sqlQuery & ", overview.[Rule Group], rules.RulegroupID"
    sqlQuery = sqlQuery & "FROM (overview INNER JOIN relationship ON overview.id=relationship.id) "
    sqlQuery = sqlQuery & "INNER JOIN rules ON relationship.rulesID=rules.ID"
    sqlQuery = sqlQuery & "WHERE " & field & " IS NOT NULL;"
    Me.RecordSource = sqlQuery
    Requery

    debugText = "New SQL Query = " & sqlQuery
End Sub

Thanks.

Edit: Resolved, not sure how to respond to own question...