Hi Alma,
Generally, this is not possible because TestComplete emulates user's actions against the tested application and like two users cannot work simultaneously within one user session so TestComplete is not intended to press two different buttons simultaneously, for example.
You may consider distributed testing functionality provided by TestComplete (
http://support.smartbear.com/viewarticle/55046/) if you need to test, for example, what happens if two users simultaneously submit changes to the same some record.