HTML code as text in Excel

I have an Excel file that will be saved as an .csv file for importation into an email automation system. In a function I need to return a piece of HTML code as text.

=IF(A2<0,"CHECKMARK CODE",A2)

The "CHECKMARK CODE" needs to be replaced by:

< span style="font-size:16px">& #10003;.

For this post, spaces were added to prevent code from display as a checkmark.

However, all my attempts at format_text function or adding apostrophes only yields errors.

How do I return this as text exactly as needed by the email automation system?