How to create multiple xValueMembers in ASP Chart control

I have a chart control that looks like the attached image.  The control consists of 3 series and is bound to a dataset.  The xValuMember is bound to the "AcctName" column.  But what I need to do is combine the data in the AcctName column with the data in the AcctNumber column so my xvaluemember label is not just the account name but under it is the account number.


thanks in advance for the help.