\' Удаляем.\n    With ThisWorkbook.VBProject.VBComponents("Лист1").CodeModule\n        .DeleteLines  1 , .CountOfLines\n    End With

Set vbc = ThisWorkbook.VBProject.VBComponents("Лист1")

    Dim wb As Workbook
    Dim cm As CodeModule
    Dim strPath As String
    Dim idx As Long
    
    strPath = "D:\Temp\Книга1.xls"
    
    Set wb = Application.Workbooks.Open(strPath)
    Set cm = wb.VBProject.VBComponents("Лист1").CodeModule
    
    With cm
        .DeleteLines  1 , .CountOfLines
        idx =  1 
        .InsertLines idx, "Sub Test()"
        idx = idx +  1 
        .InsertLines idx, "Msgbox ""Test!"", vbInformation"
        idx = idx +  1 
        .InsertLines idx, "End Sub"
    End With
    
    Set cm = Nothing
    Set wb = Nothing