Kinda hard to understand what you meant. You're talking about someone saying something, and then stepping on or touching a brick to cause something to happen because they said a certain thing in chat, right?
0 | onPlayerTouch | Self | VCE_ifValue | <var:cl:lastmsg> | == | what player says to make stuff happen | 1 1
1 | onVariableTrue | Client | centerPrint | asdf
VCE is required for that, obviously.