if each cell in column A relates to a cell in the same row,but in column B you could use this macro. (to insert rightckick on the sheettab, choose show code and paste the code)
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 4 Then
Select Case Target.Value
Case 1: ci = 1
Case 2: ci = 3
Case 3: ci = 5
Case 4: ci = 7
Case 5: ci = 9
Case 6: ci = 11
Case 7: ci = 13
Case 8: ci = 15
Case 9: ci = 17
Case 10: ci = 18
Case Else
End Select
Target.Offset(0, -3).Interior.ColorIndex = ci
End If
End Sub