How to read a (SharePoint) custom web part property before the page loads?

Question

I have a custom web part in SharePoint that has one property. Here is it:

    // Specify report path 
    private string _report_path = string.Empty;
    [WebBrowsable(true),
    Personalizable(true),
    WebDisplayName("Enter Path"),
    WebDescription("Embeds an OBIEE Report in the portal"),
    SPWebCategoryName("Report")]
    public string ReportPath
    {
        get { return _report_path; }
        set { _report_path = value; }
    }

The problem is that I have to refresh the page manually a second time for the property to get set. Apparently, I need to put the method inside a PreRender event. Does anyone know how I can do this? Thanks.