I have the following code, but he replaces also the numbers which were
already replaced.
How can I prevent that he will replace the cells which were already
replaced?
Maybe I can do it with a complete number or something like that?

This is my code:
Columns("F:F").Select
Selection.Replace What:="1", Replacement:="0", LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="2", Replacement:="10", LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="3", Replacement:="15", LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="4", Replacement:="20", LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="5", Replacement:="v.a. 20",
LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="6", Replacement:="v.a. 25",
LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="7", Replacement:="v.a. 35",
LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="24", Replacement:="v.a. 20",
LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="X", Replacement:="v.a. 20",
LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="Y", Replacement:="v.a. 25",
LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False
Selection.Replace What:="Z", Replacement:="v.a. 25",
LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False