Run macro file from Word

[jsk.choi]

is there a way to store code in a text file, then call that text file
from Word?

i'm using some simple code to draft commonly used letters in the
office, but as of right now, the same code is pasted into each of the
letters (there are about 15 different letters that all use the same
code).

so, everytime i make a change to the code, it needs to be re-copied
into all forms.

so, is there a way to store this code in one location (a text file),
then have the different forms call this file?

thanks.