NullReference exception unhandled by user code

Hi guys,
 
I'm working on having two forms that communicate together. In order to do this, I am passing public value from the source page. Here's how I did it:
In the source page I have:
Public ReadOnly Property CurrentCity() As String
        Get
            Return txtboxfake.Text
        End Get
    End Property

 
Then under page_load of the page I have:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 
        txtteam.Text = PreviousPage.CurrentCity
 
        txtboxdate.Text = Calendar1.SelectedDate
 
    End Sub
For some reason I keep getting an error that says "NullReference exception unhan ...