That was useful to understand how I can manually raise these events....
However, aparantly I am not really navigating the data as I presumed previously.

I just tried the following

    Private Sub CompanySelectionUltraCombo_ValueChanged _
    (ByVal sender As Object, ByVal e As System.EventArgs) _
    Handles CompanySelectionUltraCombo.ValueChanged

        Dim companySelectedRowIndex As Integer = _
            Me.CompanySelectionUltraCombo.SelectedRow.Index
        Me.BindingContext.Item(oCompanyList).Position() = companySelectedRowIndex
        Me.oCompanyList.CallStateChange(mmBusinessState.Navigated)

    End Sub

When the state change was called it correctly called my Business Object's HookParentNavigated HOWEVER, the value of e.PrimaryKevValue is not changing to match the value selected in the ComboBox.

    ' Parent Navigated hook method
    Protected Overrides Sub HookParentNavigated _
    (ByVal bizObj As mmBusinessObject, ByVal e As mmBusinessStateChangeEventArgs)
        Me.GetCompanyByCompanyId(e.PrimaryKeyValue)
    End Sub

I am apartently missing a binding process somewhere...
Do I have to rebind the control after the selected index changes or what else should I consider?