exact width heigth string

Some years ago i wrote this script to calculated the dimensions of a text.
I would like tot use character.rages instead of measure.string.
Is this possible in this script?
Groeten,
Adri
 
<%@ Page Language="C#" trace="false" Explicit="true" aspcompat="true" Debug="true" %>
<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Text" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Imaging" %>
<%@ Import Namespace="System.Drawing.Text" %>
<%@ Import Namespace="System.Drawing.Drawing2D" %>