ciao ho provato a fare come dici tu

strSql1 = "SELECT COUNT(*) AS PAGECOUNT FROM (SELECT newsid, news, titolo, fonte FROM articoli UNION SELECT newsid, news, titolo, fonte FROM leggi)"
set rsCount = my_Conn.Execute(strSql1)

ma mi da il seguente errore

Microsoft OLE DB Provider for ODBC Drivers error '80040e09'

[TCX][MyODBC]You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT newsid, news, titolo, fonte FROM articoli UNION SELECT


???

Grazie