A word of warning - the HTML 'marquee' tag has been obsolete and deprecated for at least 10 years:
This was something Microsoft invented during the browser wars with Netscape Navigator nearly 20 years ago. It has never been adopted as part of the web standards.
It would be very unwise to use it in a public-facing website. At best it will be really buggy - at worse it will not work at all and your website users will not see your text. Don't waste your time with it.
You should really look at using a jQuery text scrolling effect. A quick search of Google reveals many, like this one:
It is MIT licensed. You could download the HTML, CSS and JS components and then reassemble it in RapidWeaver using my free Builder stack.