About CheckBoxList Control ...

[Kylin]

I have a CheckBoxList ,
and I bind this controls from a database,
cblxx.DataSource=xxData ;//dataset
cblxx.DataValueField="xx_Field";
cblxx.DataTextField="xxx_Field";
cblxx.DataBind();

now I have a a string like "1,2,3,4,5,6,7"
and the string inclue the xx_field ,
how can I bind the string to the checkboxlist ,
and if the string include the xx_field,
the item is checked ,
if not ,the item is uncheck ?

do I declare my meaning clearly ?
any help ?
thanks a lot !