Validators and Datagrid

Validators are usually attached to a specific control so conceptually it does not fit very well in this scenario - you are not interested in the value of each control but rather in at least one of them being checked therefore i would rather create a javascript and attach it to the control doing the post.

You can, of course, create your own validator control doing this job but it would by quite a complex way to achieve this.
I doubt you can achieve this using available validators.