Lily,
It doesn’t affect the choice of the network : the CBQ serves to distinguish among several cells within the *same* network !
The network selection is performed earlier, and it depends on network preferences (“friendly” neighbours chosen first) + RxLev. Nothing much you can change there.
the only thing you can do is put the RXLEV ACCESS MIN to the lowest value possible, and the MS TX PWR MAX CCH to 33dBm. (and not 43dBm, as I have often seen on networks…)