Change frame contents on rollover


Could any kind soul tell me how to change this:

<li><a href=“<% =image %>” title=“<% =title %>” target=“mainFrame”><img src=“<% =tn %>” border=“0”/> </a></li>

…from a standard link into a rollover? I’ve got a batch of thumbnails (tn) in the left frame (populated by vbScript) which load larger images (image) into the right-hand frame on click. I’m not sure of the syntax to do this. Would I, for example, have to use a Javascript or vbScript function, like this:

<li><a href=# onmouseover imgFrame(“<% =image %>”,“<% =title %>”><img src=“<% =tn %>” border=“0”/> </a></li>

function {
[Javascript to open image in right-hand frame]

…or can I do it with HTML in the <a href>?

Any pointers gratefully received.

Thanks for your time.