Hi,
you can access the value of the multiline box using javascript using this code:
<?xml version="1.0" encoding="UTF-8"?>
<xp:view xmlns:xp="http://www.ibm.com/xsp/core">
<xp:inputTextarea id="inputTextarea1" value="123"></xp:inputTextarea>
<xp:scriptBlock id="scriptBlock1">
<xp:this.value><![CDATA[var elem = dojo.byId('#{id:inputTextarea1}');
alert( elem.value );]]></xp:this.value>
</xp:scriptBlock>
</xp:view>
Hope this helps,
Sven