You can delete that from the 'auto-correct' list. From the menu bar, select
Tools Options, click the Spelling tab, then Auto Correct Options. Scroll
down til you see the offending entry, highlight it and click Delete.

"Q1" wrote:

How can I make Excel STOP converting 3 consecutive periods (input a three
separate characters) into an ellipse (single character)? The external data I
am importing uses each period as a place holder in a 18 alpha-numeric
character sequence, if there is no alpha or numeric for that position, it
uses a period - which when there are three consecutive period, Excel converts
it into the ellipse (one character).