asp.net 4.5 checkbox & saving/retrieving viewstate (persist value of checkbox) c#

So ... I have a checkbox on my aspx page

        <asp:CheckBox ID="chkHideHighlights" runat="server" 
        Text="Hide Parameter Hightlights" AutoPostBack="true" 
        OnCheckedChanged="chkHideHighlights_CheckedChanged" 
        ViewStateMode="Enabled"  />

The change event runs a tiny bit of code to change the name of a stored procedure called w/in the page & to refresh the form holding the values returned from the sp

        protected void chkHideHighlights_CheckedChanged(object sender, EventArgs e)
    {
        if (chkHideHighlights.Checked.Equals(true))
        {
            sqlGetHTML.SelectCommand = "Customer_Contact_output.SP_EMAIL_PREVIEW_NOCOLOR";
            divHighlight.Visible = false;                
        } 
        else
        {
            sqlGetHTML.SelectCommand = "Customer_Contact_output.SP_EMAIL_PREVIEW";
            divHighlight.Visible = true;
        }

        frmEmail.DataBind();           
    }

The frmEmail control contains data elements populated by calling the SP based on a dropdownlist control change event

I'm desperately trying to find how I can both save the state of the checkbox as well as which SP was set for calling.

I've been trying to mess with ViewState.Add(..) so far I have this:

ViewState.Add("chkHideHightlights", chkHideHighlights.Checked.ToString()); 

I DO see the values getting written to ViewState ("True" and "False") - btw, it's marked as IsDirty ?

Where I'm stuck is - I'm assuming within the Page_Load I need to check if a value is there & both be able to set (persist) the check box (it always unchecks on ddl change) and (depending on the state of the checkbox) set the SelectCommand on the sql control.

I feel so close - most of my searches come up with .net 2.0 examples :(

Ideas? Help? Thnx in advance.