Select case

Private Sub Unite_3(Plage$, chaine1$, chaine2$)
Dim c As Range, unit As Range
Set unit = Range(Plage)
For Each c In unit
If Len(c) > 0 Then
If InStr(chaine1, c.Text) > 0 Then
c.Offset(, 2).Value = 100000
c.Offset(, 2).Interior.ColorIndex = 12
ElseIf InStr(chaine2, c.Text) > 0 Then
c.Offset(, 2).Value = 200000
c.Offset(, 2).Interior.ColorIndex = 10
Else
c.Offset(, 2).Interior.ColorIndex = 4
End If
End If
Next
End Sub

Sub Test()
Unite_3 "B16:B70", "m²mlm3u", "ens"
End Sub

  Dim Dl As Long, Cherche As Range, C As Range
  Dl = Cells(Rows.Count, 1).End(xlUp).Row
  For Each C In Range("A12:A" & Dl).SpecialCells(xlCellTypeConstants)
    Set Cherche = Columns("C:AA").Find(C, LookIn:=xlValues, LookAt:=xlWhole)
    If Not Cherche Is Nothing Then
      Select Case Cherche.Column
      Case 3
        C.Offset(0, 1).Value = "10 0000"
        C.Offset(0, 1).Interior.ColorIndex = 12
      Case 4
        C.Offset(0, 1).Value = "20 0000"
        C.Offset(0, 1).Interior.ColorIndex = 10
      Case Else
        C.Offset(0, 1).Interior.ColorIndex = 4
      End Select
    End If
  Next