Try the following and check X & Y values in lines Case X to Y

HTH
--
AP

'---------------------------
Private Sub Worksheet_Change(ByVal Target As Range)

'Agrandir la plage verticalement selon les besoins
Const myRangeAddr As String = "B:B"
Dim oCell As Range

If Intersect(Target, Range(myRangeAddr)) _
Is Nothing _
Or Target.Count 1 _
Then
Exit Sub
End If

Set oCell = Target.Offset(0, -1) ' Column A

Select Case Target.Value

Case vbNullString
oCell.Interior.ColorIndex = xlNone
oCell.Font.Bold = False

Case Is < -10
oCell.Interior.ColorIndex = 3
oCell.Font.Bold = True
oCell.Borders.ColorIndex = 1

Case -10 To -5
oCell.Interior.ColorIndex = 46
oCell.Font.Bold = True
oCell.Borders.ColorIndex = 1

Case -5 To -0.5
oCell.Interior.ColorIndex = 44
oCell.Font.Bold = True
oCell.Borders.ColorIndex = 1

Case 2 To 5
oCell.Interior.ColorIndex = 35
oCell.Font.Bold = True
oCell.Borders.ColorIndex = 1

Case 5 To 10
oCell.Interior.ColorIndex = 4
oCell.Font.Bold = True
oCell.Borders.ColorIndex = 1

Case 10 To 1000
oCell.Interior.ColorIndex = 10
oCell.Font.Bold = True
oCell.Borders.ColorIndex = 1

Case Else
oCell.Interior.ColorIndex = xlNone
oCell.Font.Bold = False

End Select

End Sub