Fijate si esto te sirve.
Código asp:
Ver originalstrSQL = "SELECT * FROM basedadatos where producto like '%" & (Request("producto")) & "%' and marca like '%" & (Request("marca")) "
Select case lcase(request("sexo"))
case "hombre"
case "mujer"
strSL = strSQL & " AND (sexo ='"&Request("sexo")&"' OR sexo = 'ambos') "
case "ambos"
case "nenes"
strSL = strSQL & " AND sexo = '&Request("sexo")&' "
End Select
Saludos