There is a total packets/bytes transfer page in the router firmware - off the tools menu as I recall - but it gets reset on every router reboot... you could make a point of counting it once a day or so - not ideal, I know.

If D-Link provided access to (for example) an SNMP MIB in the router, you could inquire the numbers from it using all sorts of (perhaps even free) software on your PC, but I don't know if D-Link included one and/or how/if they'd let you get at it. Be nice to know, don't you think?
To be honest, I've not seen this feature included on a D-Link (or for that matter ANY) consumer level networking device... You got to pay for a more capable unit to get at that kind of feature.
Another thought - not practical for most people at home - but you could put a Linux PC running some firewall software (plenty of options there too) between the Broadband modem and the router and just let it pass packets on an uninterrupted basis and count the metrics off there.
