In a document, I type a word such as ##LastName##. This is typed is sequence, no move of the mouse, keys being pressed one after the other. However, Word decides to format it as it sees fit:

<w:r>
<w:t>##</w:t>
</w:r>
<w:proofErr w:type="spellStart"/>
<w:r>
<w:t>LastName</w:t>
</w:r>
<w:proofErr w:type="spellEnd"/>
<w:r>
<w:t>##</w:t>
</w:r>

This causes a problem as I need to replace a specific string ##LastName## but it won't work.

How to avoid Word doing this?