UserControl is "Nothing"?

I am trying to pass one of three different kinds of UserControls into the below SubProcedure and based on the value of the "testType" parameter, the "uc" will get set accordingly. My problem, however, is that the value of "uc" is Nothing when it enters the Try Catch even though it was assigned as a "userLoad", "userCreep" or "userRepeat" UserControl. How can I capture the appropriate UC when passed in?

Thanks!

    Private Sub ValidateLoadEnvironmentValues(uc As UserControl, testType As String)

        Select Case testType
            Case "Load"
                uc = DirectCast(uc, userLoad)
            Case "Creep"
                uc = DirectCast(uc, userCreep)
            Case "Repeat"
                uc = DirectCast(uc, userRepeat)
        End Select

        Try
            EH.ErrorMessage = String.Empty

            GetEnvironmentReadings(uc, testType)

            If EH.ErrorMessage = String.Empty Then
                AreTestsComplete(uc)
            End If

ProcessMessage:

        Catch ex As Exception
            EH.ErrorMessage = "frmCalibration_3/ValidateLoadEnvironmentValues() - " & ex.Message & "...Contact Engineering!" & "~E"
        End Try
    End Sub

Select allOpen in new window