Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" _
(ByVal lpBuffer As String, nSize As Long) As Long
Private Sub UserForm_Initialize()
Dim lpBuff As String * 25
Dim ret As Long, UserName As String
ret = GetUserName(lpBuff, 25)
UserName = Left(lpBuff, InStr(lpBuff, Chr(0)) - 1)
CommandButton1.Visible = IIf(Not IsError(Application.Match(UserName, _
Sheets("Feuil1").Range("A1:A" & Sheets("Feuil1").[A65000].End(xlUp).Row), 0)), True, False)
End Sub