Is it possible to handle "on focus" and "on focus lost" events on text fields?

Basically, currency fields from sharepoint lists are represendted as simple number fields inside spform forms. Our clients insist on these fields showing money amounts in currency format when cursor is not in the textbox, and as a regular number when cursor is in the textbox.

As I'm only aware of fd.field.change event I'm wondering if there's a way of doing this at all?

Thanks