Hi all,
What the purposes of private-key under access list, when I read about this in wireless guide I thought can apply private Key (WEP key) for each client (its very good if possible applicable) but it didn’t success 
Also I didn’t find enough resources for this case, just the following explanation :
Access List Property Description
ap-tx-limit (integer; default: 0) - limits data rate for this wireless client (in bps)
0 - no limits
authentication (yes | no; default: yes) - whether to accept or to reject this client when it tries to connect
client-tx-limit (integer; default: 0) - limits this client’s transmit data rate (in bps). Works only if the client is also a MikroTik Router
0 - no limits
forwarding (yes | no; default: yes) - whether to forward the client’s frames to other wireless clients
interface (name) - name of the respective interface
mac-address (MAC address) - MAC address of the client
private-algo (104bit-wep | 40bit-wep | none) - which encryption algorithm to use
private-key (text; default: “”) - private key of the client. Used for private-algo
skip-802.1x (yes | no) - not implemented, yet
Notes
If you have default authentication action for the interface set to yes, you can disallow this node to register at the AP’s interface wlanN by setting authentication=no for it. Thus, all nodes except this one will be able to register to the interface wlanN.
If you have default authentication action for the interface set to no, you can allow this node to register at the AP’s interface wlanN by setting authentication=yes for it. Thus, only the specified nodes will be able to register to the interface wlanN.
Example
To allow authentication and forwarding for the client 00:01:24:70:3A:BB from the wlan1 interface using WEP 40bit algorithm with the key 1234567890:
[admin@MikroTik] interface wireless access-list> add mac-address=
... 00:01:24:70:3A:BB interface=wlan1 private-algo=40bit-wep private-key=1234567890
[admin@MikroTik] interface wireless access-list> print
Flags: X - disabled
0 mac-address=00:01:24:70:3A:BB interface=wlan1 authentication=yes
forwarding=yes ap-tx-limit=0 client-tx-limit=0 private-algo=40bit-wep
private-key=“1234567890”
Again I said with many and different experiments and options, but no successful to make Private Key for each client by this option
So first I hope from the moderators and experts to explain and said his opinions on this case.
Regards