ADSL and serial line aggregation

Hi all,

Is it possible to have a router with a serial link and an ADSL link that aggregate all together so the ADSL provide more bandwidth when the serial overload ? I mean there might be a VPN between the two ADSL that establish to complement the serial, then the two endpoint aggregate to form just one point-to-point link.

Do you think it's possible ?

Thanks.

-- dominix