Pass public variable to Sub

[vbmalik12345]

Public strSubject As String
Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
strSubject = Item.Subject
MsgBox (strSubject)
UserForm1.Show
End Sub

Private Sub ButtonOK_Click()
MsgBox strSubject
End Sub

This is a test program. I want to pass the value in var strSubject to the form when i click a button.

When i click the button it showing empty.. Could someone help how to pass a public variable to sub