advapi32dll

getusername这个函数是大小写敏感，GetUserNameA才对：

Private Declare Function getusername Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpbuffer As String, nsize As Long) As Long

调用的时候用GetUserName

或者：

Private Declare Function GetUserNameA Lib "advapi32.dll" (ByVal lpbuffer As String, nsize As Long) As Long

调用的时候用GetUserNameA调用就ok

你遇到的问题应该是"找不到入口点‘getusernamea’ in 'advapi32.dll' "

调用api的时候大小写一定要匹配（至少在alias中一定要匹配）就没问题，要不然是不能执行的（因为找不到这个名字）