Alex is quite right. You can´t easily switch between sequencer/arranger in the same song. But you are able to do it the way I described earlier; make the sequenced part a part of a style. I´m not sure I understood your question, but the sequenced part is played with all the chord changes and everything. This means that you must not change chords yourself when the sequenced part is playing. But of course You have to trigger one initial chord to get the right tune! If you create your stylepart in C then you have to trigger a C to make it play the way you want. If you trigger an F, it will play correctly with chord changes and everything - but in an other tune!

Regards, Michael