Hold scan results for a period of time

[COFM]

Hi!

If i command "# iwlist wlan0 scanning", i can get the scanning results from 
the monitor.
Now i do scan at time1, i can get ap information at that time1.
Later, i do scan again at time2, then i can get new ap information at that 
time2.
It seems that the ap information i got just the results at time2, not 
include the results at time1.
If AP1 is alive at time1, but inactive at time2. Thus i can't get the 
information about AP1 finally.

When i need to do roaming, i want to refer the previous information.
How can i hold the scan results for a period of time?

Any help would be greatly appreciated

Thanks,
Sevesdion