Looks like I solved the Question myself.
Usefull if you enter the same number twice on the same row.
It's esay to do

Sub LookDoubleAgain()
For Each c In Range("C2:V2201")
If c.Value = Cells(c.Row, c.Column + 1).Value Then
Range(c, c.Offset(0, 1)).Select
With Selection.Interior
.ColorIndex = 15
.Pattern = xlSolid
End With
End If
Next
Range("A1").Select
End Sub

Hopes this helps someone!