This is what i have so far, but I am obviously getting an error. 

try
{
    dblNights = Convert.ToDouble(txtNights.Text);
 
    if (dblNights > 1 && 14)
    {
    }
    else
    {
        string script = "alert(\"Number of Nights Must be between 1 and 14!\");";
        ScriptManager.RegisterStartupScript(this, GetType(), "ServerControlScript", script, true);
        txtNights.Focus();
    }
}//End Try
 
catch
{
    string script = "alert(\"Number of Nights Must be an Integer!\");";
    ScriptManager.RegisterStartupScript(this, GetType(), "ServerControlScript", script, true);
 
    txtNights.Focus();
}//End Catch

I am not quite sure what to do to make show an error box if numbers besides 1-14 are entered. Everything else is working, just not that. What am I doing wrong? 

Thank you.