About D-Link Router

HI,
I have 64 kbps leased line connection,also i hv dlink 1162 router with leased modem.I want my users can only use 100 MB space.They can’t use more than that.Or in simple means i want to assign 4 or 5 kbps to every user.Is there any free softwarefor this.
With regards.
Anurag.