This should probably work:
Mind Switch
Enchantment [Mind-Affecting]
Level: Wiz/Sor 7
Components: V
Casting Time: 1 action
Range: Medium (100 ft. +10 ft./level)
Target: You and one other living Medium-size or smaller creature
Duration: Until you return to your body
Saving Throw: Will negates (see text)
Spell Resistance: Yes
The spellcaster can attempt to take control of a nearby living creature, forcing its mind (and soul) into the caster’s body. The spellcaster may move his or her mind back into his or her own body whenever he or she desirse (which returns the subject’s mind to its own body). The power ends when the spellcaster sends his or her mind back to his or her own body.
Attempting to switch minds is a full-round action. It is blocked by protection from evil or a similar magical ward. The spellcaster possesses the body and forces the creature’s mind into the spellcaster’s body unless it succeeds at a Will save.
If successful, the spellcaster’s life force occupies the host body, and the host’s life force takes over the spellcaster’s. The spellcaster can call on rudimentary or instinctive knowledge of the subject creature, but not upon its real or acquired knowledge. Each retains his or her own alignment, Intelligence, Wisdom, and Charisma scores, class, level, skills, base attack bonus, base saving throw bonuses, and hit points (regardless of new Constitution score). Each gains the new body’s Strength, Constitution, and Dexterity scores (including modifiers based on these abilities), as well as natural (but not magical) armor. Neither gains the other’s special abilities.
As a standard action, the spellcaster can return to his or her own body, if within range (which ends the power).
If the spellcaster's new body is slain, he or she returns to his or her own body, if within range, and the life force of the original body departs. If the new body is slain beyond the range of the power, the spellcaster dies, but the switched creature lives on in the spellcaster’s body permanently. If the spellcaster’s body is slain while inhabited by the target's mind, the target dies, and the spellcaster continues to inhabit the new host body permanently. Any life force with nowhere to go is treated as slain.
A successful targeted dispel magic on either switched body causes both minds to return to their original bodies, if within range. If they are out of range, the dispel has no effect.