This LISP routine from Dale Miksch allows you to change the size of multiple text entities at once. Start by loading the routine, then type in the command TSZ. The default method of this routine prompts you for a selection of text, mtext, and even rtext (created by the Express Tool of the same name). After you enter a new text height, the selected objects will be modified. There is a second option where you enter the old size first, then enter a new size without making a selection. In this case, all text entities that match the old size will be modified. This latter method does not work on mtext or rtext.