Newbie Alert - populating form fields

Not only new to PHP, but new to programming too, so please bare with me:) I have a form that I want to populate with data from one table and insert into another table. I've managed so far to populate a drop down menu from the first table, but how do I populate the other fields once one of those items is selected? What I have so far is the drop down menu: <? $query = "select * from Courses"; $result = mysql_query($query); $num = mysql_numrows($result); echo "<font face=\"Arial\">Please choose the course you would like to schedule:</font><br><br>"; echo "<font face=\"Arial\" color=\"blue\">Course:</font><br>"; echo "<select name=\"Course\"Course_ID=Course_ID>"; echo "<option value='' selected>***Select a Course***</option>"; /*Dynamically generate drop-down list*/ $i=0; while ($i<$num): $hello = mysql_result($result,$i, "CourseTitle"); echo "<option value='$hello'>$hello</option>"; $i++; endwhile; echo "</select><p>"; ?> and a field; Audience:<br></font><textarea name="Audience" rows="5" cols="25" wrap><? echo "$Aud"; ?></textarea></td> Will someone please point me in the right direction for tutorials or scripts or whatever on how to code "if Course A is selected, than Audience= $Audience from table Courses where Course A = Course A". I know I'm missing something fundamental here and I'm running out of time before deadline! TIA Beth