put a macro with this
Note : for sample i have compared B & c columns in same sheet
Sub tst()
For Each opic In Me.Pictures
opic.Delete
Next
For i = 6 To 28
Cells(i, 8).Activate
If Cells(i, 2) > Cells(i, 3) Then
ActiveSheet.Pictures.Insert ("C:\up.bmp")
Else
ActiveSheet.Pictures.Insert ("C:\down.bmp")
End If
Next
End Sub