Attribué une valeur a un choix de Combobox VBA

Private O As Worksheet
Private COL As Byte
Private LI As Integer

Sub userform_initialize()
Dim CTRL As Control

Set O = Sheets("parame")
For Each CTRL In Me.Controls
    If CTRL.Tag <> "" Then
        COL = CByte(CTRL.Tag)
        LI = O.Cells(Application.Rows.Count, COL).End(xlUp).Row
        CTRL.List = O.Range(O.Cells(9, COL), O.Cells(LI, COL)).Value
        If CTRL.Tag = 11 Then CTRL.List = IIf(CTRL.Name = "ComboBox5", O.Range("K9:K11").Value, O.Range("K12:K14").Value)
        CTRL.ListIndex = 0
    End If
Next CTRL
ComboBox1.Visible = OptionButton5.Value
ComboBox2.Visible = OptionButton6.Value
ComboBox3.Visible = OptionButton7.Value
OptionButton6.Value = True
End Sub

Private Sub CommandButton1_Click()
Dim longeur As Double, largeur As Double, surface As Double, epaisseur As Double, volume As Double

For I = 2 To 4
    If Me.Controls("TextBox" & I).Value = "" Then MsgBox "Vous devez renseigner ce champ !": GoTo suite
    If Not IsNumeric(Me.Controls("TextBox" & I).Value) Then
        MsgBox "Vous devez rentrer une valeur numérique !"
    Else
        If CDbl(Me.Controls("TextBox" & I).Value) <= 0 Then MsgBox "Vous devez rentrer une valeur positive !"
    End If
suite:
    With Me.Controls("TextBox" & I)
        .SetFocus
        .SelStart = 0
        .SelLength = .Value
    End With
    Exit Sub
Next I

For I = 1 To 3
    If Me.Controls("ComboBox" & I).Visible = True Then
        LI = Me.Controls("ComboBox" & I).ListIndex + 9
        COL = CByte(Me.Controls("ComboBox" & I).Tag)
        Exit For
    End If
Next I

matériau = CDbl(O.Cells(LI, COL + 1))
longeur = CDbl(TextBox2.Value)
largeur = CDbl(TextBox3.Value)
epaisseur = CDbl(TextBox4.Value)                                         

'Insertions des variables

Workbooks.Add                                                'Fais apparaitre un nouveau classeur

ActiveSheet.Name = ("devis")                                  'La Feuille du nouveau classeur se renomme en "devis"
Range("G3").Select
ActiveCell.FormulaR1C1 = TextBox1                           'Mise en forme du titre du devis
Range("G3:L3").Select

With Selection.Font
.ThemeColor = xlThemeColorAccent1
End With

With Selection
.HorizontalAlignment = xlCenter
.VerticalAlignment = xlBottom
.ReadingOrder = xlContext
End With

With Selection.Borders(xlEdgeTop)
.LineStyle = xlContinuous
.Color = -16777024
.TintAndShade = 0
.Weight = xlMedium
End With

With Selection.Borders(xlEdgeBottom)
.LineStyle = xlContinuous
.Color = -16777024
.TintAndShade = 0
.Weight = xlMedium
End With

With Selection.Borders(xlEdgeRight)
.LineStyle = xlContinuous
.Color = -16777024
.TintAndShade = 0
.Weight = xlMedium
End With

With Selection.Borders(xlEdgeLeft)
.LineStyle = xlContinuous
.Color = -16777024
.TintAndShade = 0
.Weight = xlMedium
End With

surface = longeur * largeur                                 'Calculs, puis inscriptions dans les cellules

prixsurface = surface * materiau
Worksheets("devis").Range("F10").Value = CStr(prixsurface)
volume = longeur * largeur * epaisseur
prix = surface
End Sub