Comme ceci alors, c'est la feuille "TAV" qui sert de référence, à adapter :
Sub calcul()
Dim Plage_Nom1 As Range
Dim Plage_Nom2 As Range
Dim Plage_Nom3 As Range
Dim Nom As String
Dim Date_Mois As Byte
Dim i As Integer
Dim Total_1 As Integer
Dim Total_2 As Integer
Dim Total_3 As Integer
Set Plage_Nom1 = Worksheets("TAV").Range("A4:A14")
Set Plage_Nom2 = Worksheets("VAT").Range("A4:A14")
Set Plage_Nom3 = Worksheets("TAT").Range("A4:A14")
Nom = UserForm1.TextBox2.Text
Date_Mois = Month(UserForm1.TextBox1.Value)
i = 2
If Month(Worksheets("TAV").Cells(3, i).Value) <> Date_Mois Then
While Month(Worksheets("TAV").Cells(3, i).Value) <> Date_Mois
i = i + 1
Wend
Else
While Month(Worksheets("TAV").Cells(3, i).Value) = Date_Mois
Total_1 = Total_1 + Plage_Nom1.Find(What:=Nom, LookAt:=xlWhole).Offset(0, i - 1).Value
Total_2 = Total_2 + Plage_Nom2.Find(What:=Nom, LookAt:=xlWhole).Offset(0, i - 1).Value
Total_3 = Total_3 + Plage_Nom3.Find(What:=Nom, LookAt:=xlWhole).Offset(0, i - 1).Value
i = i + 1
Wend
End If
While Month(Worksheets("TAV").Cells(3, i).Value) = Date_Mois
Total_1 = Total_1 + Plage_Nom1.Find(What:=Nom, LookAt:=xlWhole).Offset(0, i - 1).Value
Total_2 = Total_2 + Plage_Nom2.Find(What:=Nom, LookAt:=xlWhole).Offset(0, i - 1).Value
Total_3 = Total_3 + Plage_Nom3.Find(What:=Nom, LookAt:=xlWhole).Offset(0, i - 1).Value
i = i + 1
Wend
UserForm1.TextBox3.Text = Total_1
UserForm1.TextBox4.Text = Total_2
UserForm1.TextBox5.Text = Total_3
End Sub