Using textboxes to change text within an already preset HTML document

[The1One]

I've got this code that I can change accordingly if anything is needed:\[code\]<object width="544" height="445" type="application/x-shockwave-flash" data="http://internal.kongregate.com/gamez/0002/0692/live/SkystoneLoaderOffsite_linkbar2.swf?kongregate_game_version=1279736137" id="gamediv"><param name="bgcolor" value="http://stackoverflow.com/questions/14427933/#140a08"><param name="allownetworking" value="http://stackoverflow.com/questions/14427933/all"><param name="allowscriptaccess" value="http://stackoverflow.com/questions/14427933/always"><param name="base" value="http://internal.kongregate.com/gamez/0002/0692/live/"><param name="flashvars" value="http://stackoverflow.com/questions/14427933/kongregate=true&kongregate_username=IgnorantMasses&kongregate_user_id=7388796&kongregate_game_id=20692&kongregate_game_version=1279736137&kongregate_host=http%3A%2F%2Fwww.kongregate.com&kongregate_game_url=http%3A%2F%2Fwww.kongregate.com%2Fgames%2FFliplineStudios%2Fremnants-of-skystone&kongregate_api_host=http%3A%2F%2Fapi.kongregate.com&kongregate_game_auth_token=eacd29116b05030ae42292feb5278da7d6135d126e92ed946a0c843e2c105b89&kongregate_stamp=eacd29116b05030ae42292feb5278da7d6135d126e92ed946a0c843e2c105b89&api_path=http%3A%2F%2Finternal.kongregate.com%2Fflash%2FAPI_AS3_5300b6d7b0b219c38360c3b76c40eb14.swf&game_url=http%3A%2F%2Fwww.kongregate.com%2Fgames%2FFliplineStudios%2Fremnants-of-skystone&kongregate_api_path=http%3A%2F%2Finternal.kongregate.com%2Fflash%2FAPI_AS3_5300b6d7b0b219c38360c3b76c40eb14.swf&kongregate_channel_id=1358695625405&debug_level=undefined"></object>\[/code\]I have this code for 3 text boxes:\[code\] <h4> Put your username in the box under here</h4> <textarea id="Username"></textarea> <br > <br > <h4> Put your UserID in the box under here</h4> <textarea id="UserID"></textarea> <br > <br > <h4>Put your Authentication Token here</h4> <textarea id="Auth"></textarea> <br > <br ><button id="Play" >Play RoS</button>\[/code\]When someone puts their username/ID/Authentication Token in the boxes, then presses play, how do I get it to change the original HTML code with the informationI can use tags if needed.