Pass Variable Value To User Control From Host Page

[lmod]

I am trying to pass the value of a varible to a user control (code behind) from the host page of the user control. In the uc code behind I am using Get...Set to retrive the value and if I use a static string (i.e "blk") it works but I cannot get it to work using (<%#variable%>. Here is the code:

In the user control code behind

        Public mainSkin As String

        Public Property ucSkin() As String
            Get
                Return ucSkin
            End Get
            Set(ByVal value As String)
                mainSkin = value
            End Set
        End Property

Here is the code from the host page

<jsFlsAd:flsAd  id="FlsAd" runat="server" ucSkin= "<%#varSkin%>"></jsFlsAd:flsAd>

Where varSkin is declared as Public in the code behind of the host page.

The above line does not work, however if I change it to:

<jsFlsAd:flsAd  id="FlsAd" runat="server" ucSkin= "blk"></jsFlsAd:flsAd>

That will work.
Can someone help me understand what I am doing wrong?