Treads

Why cannot I create a thread like:
' Standard Module
Public Declare Function CreateThread Lib "kernel32" (lpThreadAttributes As SECURITY_ATTRIBUTES, ByVal dwStackSize As Long, lpStartAddress As Long, lpParameter As Any, ByVal dwCreationFlags As Long, lpThreadId As Long) As Long

Public Type SECURITY_ATTRIBUTES
nLength As Long
lpSecurityDescriptor As Long
bInheritHandle As Long
End Type
Public sec As SECURITY_ATTRIBUTES
Public ThreadID As Long

Sub Main()
Dim result As Long
Form1.Show
result = CreateThread(sec, 0, AddressOf Try, 0, 0, ThreadID)
Form1.Label1 = result
End Sub

Sub Try()
'do something

End Sub