Have you investigated content controls? At their simplest these are intended as place holders for user input text.

As Word is a style driven application rather than a text layout application, it is inevitable that text will move to accommodate the text added. If you don't want it to move, then use (borderless) frames or table cells of fixed dimensions to hold the text.

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Graham Mayor - MS MVP (Word) (2002-2019)
Visit my web site for more programming tips and ready made processes www.gmayor.com