Try something like this:

SQL> create table t as select 1 x from dual;

Table created.

SQl> alter table t allocate extent
  2    ( datafile '....' size XXX );

Table altered.

where the datafile is the one you do NOT want to use, and XXX is nearly the freespace available in that datafile. In effect you have now "filled" that datafile.

Now do your 'alter table move' in your real table. It will be moved and cannot use the space in the full datafile. Then drop table t (with the purge option).