Question:  If a user is browsing an account in SalesLogix, and is viewing the contacts in the contacts tab, I would like him/her to be able to select multiple contacts in the tab and choose a custom button that opens an email addressed to the selected contacts.

Can I make the rows selectable in a grid?

Answer: The SLXGridView is based on the GridView and does not allow multiselect.   However, you could add a column with Checkboxes to allow the user to select multiple rows.