Writing into CKEditor with javascript

Hello!

At first ,sorry for my bad english. I'm in speaking better then in writing. :)

The problem:

I have a selectbox with javascript "onchange" and want to write the content from the selected option into a textarea. This is ok, but when i change the class of the textarea to class="ckeditor", then their ist noch reaction. Has anyone a solution?

Part in the code:

			<tr>
				<td><textarea class="ckeditor" cols="110" name="text" rows="7" id="text">{$sText}</textarea></td>
				<td><select onchange="text.value = this.value;" class="selectBoxenBausteine" title="Textbaustein auswählen">
						<option value="">Textbaustein auswählen</option>
						
						{loop="$aBausteine"}
							{if="$value.grp_bereich == '2'"}
								<optgroup label="$value.grp_name}">							
									{loop="$value.bausteine"}
									<option value="{$value.bau_text}">{$value.bau_name}</option>
									{/loop}								
								</optgroup>
							{/if}
						{/loop}
						
					</select></td>
			</tr>

It's php with the "rain tpl" template engine.

I have a screenshot too. Left the CKEditor and on the right side the selectbox.

Thx for helping me. :)