Extending an AP client area

Howdy!

I have read many fine answers on here, and hope someone can help me.

I have a Cisco Aironet 1200 as my main AP with a large antenna. It lights up a very large outdoor building area. I have 25 or so clients (WET11's) that I check on (ping) with network monitoring software in it's range.

I have another 25 or so that are out of range or are on the fringe (jump on and off). A couple areas I need to light up are underground on another level.

My plan:

For the basement areas: Install a WET54G upstairs in the Cisco 1200 area. Drop a Cat5 cable to the basement and install a WAP11 to light up the basement area. The key is to have the same SSID and WEP encryption on the AP so all the monitored devices are configured the same.

For the just out of range areas: Same as above, with the WET54G in good range, and the WAP11 nearby. Again, the key is to have the same SSID and WEP encryption on the AP so all the monitored devices are configured the same. BUT - having the WET54G only connect to the Cisco is a problem because it is closer to the WAP11 and presumably will connect to it.

Are there any firmware "upgrades" for the WET54G which will allow me to tell it to only connect to the Cisco AP via it's MAC address?

Or possibly do you have another solution?

I do appreciate any help on this!