Private cls1 As New Class1
 
Private Type MyFormTyp
   X As Long
   y As Long
   Z As Long
End Type
 
Private Sub Form_Load()
   Dim mt As MyFormTyp
   mt.X = 1
   mt.y = 2
   mt.Z = 3
   cls1.TestMyClassTyp VarPtr(mt)
End Sub

Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" ( _
     ByRef Destination As Any, _
     ByRef Source As Any, _
     ByVal Length As Long)
 
Private Type MyClassTyp
   X As Long
   y As Long
   Z As Long
End Type
 
Public Sub TestMyClassTyp(ByRef st As Long)
    Dim mc As MyClassTyp
    CopyMemory mc, ByVal st, Len(mc)
 
    MsgBox mc.y
End Sub