If you don't want to manually convert the characters , use the escape() / unescape() functions available in both javascript and actionscript - you can have a look at this solution I posted ealier:
You know, I've been looking for a solution to this for a long time, posted lots of Macromedia forums but no use, and somehow, when I got here I had a feeling I'll find a solution in here, and there it is ;)
The 'escape' seems to work perfectly! Thanks very much for your time...
Just one question then... this refers when using the flashObject, now what can be done when using a plain <OBJECT> tag? like this <param name="movie" src="flashfile.swf?clickTag=http://www.mysite.com?id=1234&cat=5678">
you can either manually type the alternate (& amp;) or you can use javascript to write the entire line (using document.write). creating the entire line with javascript will give you the chance to use the escape() function.
you could also use PHP (or ASP) to write the variables as follows: