How to stop a macro Excel 5.0

Can you clarify your question ? This is how I understood it. You have an Auto_Open macro in one Workbook. In the code of that macro, you open another workbook. You then close the first workbook. From when you say 'At the moment I use the second on....' I've lost you.

Is there only one macro which is in the first workbook, or are there more ?

Try opening the sheet with the SHIFT key held down, this will not run any auto-open macros , you can then edit anything.

In fact I want the macro to stop by itself, with no human intervention. More information is needed i see :) :
Each WORKBOOK I use contains the same macros (Auto_open and others). Thess macros are :
Sub Auto_open()
    Application.OnSheetActivate = "Init"
End Sub

and calls :

Sub Init()
    Application.OnEntry = "NameOfSub"
End Sub

(...)

Then each time I enter a value, the "NameOfSub" macro is used. But I would like that each workbook uses its own macro instead of using the macro belonging to the first opened workbook.

Sorry, add the name of the module to the syntax to be certain. So...

Application.OnEntry = name of workbook file & "!" & name of module & ".NameOfSub"

You have just use more clear description of your sub:
Sub Auto_open()
Application.OnSheetActivate = ActiveWorkbook.Name & "!Init"
End Sub

Sub Init()
Application.OnEntry = ActiveWorkbook.Name & "!NameOfSub"
End Sub
Check it!

Sorry, I've not seen cartti answer.

Thanks cartti ! (and vboukhar too :) ) . See you later ... :)