Mr Happy.

Nigel got in before me, and my explanation is much the same, but you can cut and paste my example if it makes it any easier for you.

Start your new thread

Make a note of the threadid number

Go back to the old thread

Type in a line like:

<a href="thread.cfm?threadid=xxxxx">Click here</a>

...but instead of the red xxxxx put in the number you have noted.

Either use the Click here or substitute your own text.

Put whatever explanation you feel is appropriate

Submit Message and away you go.