Hello Doug:
Thanks for you help.
I know you mean,But if the table have been used,And the table name is a varible ,How to judge the table be used state.
Usually we can do like this:
if not used('tablealias')
use table alias 'tablealias' in xx
else
sele 'tablealias'
use
use table alias 'tablealias' in xx
endif

sele xx
But in that case ,What should I do?