More STA Mode Question

[imp]

Dear everyone...

I have one more question about hostap STA mode setting..
As My previous question, hostap can run as STA mode and Jouni reply kindly the answer.

> iwpriv wlan0 host_roaming 1
> iwconfig wlan0 mode managed
> iwconfig wlan0 ap <specific AP BSSID>

Yes, It really work... 
In this case, sta mode should know the specific AP's Mac address. but, in general most card utility program
remember the essid name to association near other APs (same essid, differ BSSID) in one to many situation... 
for example,
 
AP 1 (essid:test)                 AP2 (essid:test)                AP3 (essid:test)

there are three AP differ BSSID, same ESSID, in this case, above method always change the BSSID with
iwconfig wlan0 ap (BSSID) command as mannually. when it roam AP1 ->  AP2, AP2 ->AP3.

Could you recommand any way to automatically change link with near AP in sta mode hostap box ?
If so, Please give me any comment..

Best regards.. Thanks