[Greasemonkey] Adding a button to call Javascript

[Al]

I have a problem on a website that I use, where a coding error means that a
button which calls a javascript is missing.

There are other pages where the button does appear. This is the HTML for the
button...

<A HREF="JavaScript:labdomexp_PrintThermal();"><IMG BORDER="0"
SRC="/fsm/images/us/shipping/print.gif" ALT="Print" width="40"
height="15"></A>

On the page that doesn't work, the function labdomexp_PrintThermal() is
coded earlier in the HTML.

Is there a way that I can use Greasemonkey to call this javascript function?