Make it simple using a VSTi to generate chords
http://www.vst4free.com/free_vst.php?plugin=midiChords&id=1642
I use it sending midi notes to the plugin instance from a widget button to the MidiInBlock to create automated pads when change rack variations.
In the plugin you can define a diferent chord for each keyboard key, transpose the chord, and other options.
You can use a kind of “strum” to put a little delay in the chord notes to emulate a guitar.