Hola.. porque no intentas esto:
sql = "Select a.csid, a.acctname, b.aladate, b.event_time, b.code, b.descript, c.action, c.detalle from clientes as a, historia as b, detalle as c where a.csid = b.csid and b.csid = c.el_id_de_c where a.csid = '"&numero'"
Si es que csid lo tienes declarado como cadena...
SAludos
