I did this by setting up a custom bb code in the admincp with the following settings:
Code:
Title: flash
Tag: Flash
Replacement: <embed src={option} width={param} height={param} type=application/x-shockwave-flash></embed>
Example: [flash=http://www.domain.com/example.swf]400[/flash]
Description: Flash BBCode
then to add a flash to a post, use the tag:
[flash=flash file url]flash size[/flash]