CoreXY with only two Axis - homing problem

Hi there,
I need a little help for setting up my machine:

I have an Arduino Mega 2560Board, Marlin 1.1.0-RC6 and Arduino Software 1.6.8
My “Machine” is kind of kinetic art and has an coreXY setup.
I managed to get it running really cool with the Marlin Firmware, but the Problem is:
My machine has only two axis, no Z-axis no tempsensors at all – it just has to move the two
axis according to G-code. Therefore I have a problem with homig – Marlin expects to have an Z-axis.
It is possible to “tell” marlin that we have only two axis – and forget all about Z-axis?
I´, Happy for each hint.

Regards form Germany
Kai