有两个textarea我想在有光标的地方粘贴

1<form name="form1">
2<textarea name="txt1"></textarea>
3<textarea name="txt2"></textarea>
4<input onclick="document.execCommand('PASTE');" type="button" value="paste"/>
5</form>

1<form name="form1">
2<textarea name="txt1" onfocus="o=this"></textarea>
3<textarea name="txt2" onfocus="o=this"></textarea>
4<input onclick="try{o.focus();document.execCommand('PASTE');}catch(e){}" type="button" value="paste"/>
5</form>