Incrementing Datagrid Value -- Simple Question

[Ron]

I have a Datagrid that is bound to a datasource. In the table, I have a
"Next" and a "Previous" button. When the user clicks either button, I want
to display the next or previous items. My question is this: How can I
increment/decrement the value that is being bound to the datagrid?

<a href='<%# DataBinder.Eval(Container.DataItem, "officeID",
"LeaseDetails.aspx?officeID={0}") %>

How can I increment the value for "officeID"?
Thanks,

Ron