Relative path solving - tilde

Hey,
I know how this works, and that it works only in server controls.  But is there anyway I can use it in a StringBuilder:
sb.Append(String.Format("<p class=\"MsoNormal\"><a href=\"~/download.ashx?FileID={0}\">{1}</a> ({2})</p>", FileID, FileName, BasePage.ConvertFileSize(FileSize))) Thanks