Programming help : Combining 2 unit program in one unit

We have Operator interface system (LCD monitor) with CAN bus for monitoring/setting 3 phase Inverters with large capacity. We want to combine 2 unit data in one Operator interface system. Any expert programmer help me to explain how to do that or at least guide me. Our program is in C, use LCD monitor and we do not want much change in hardware.

Anyone with practical suggestion would be great help.

Thank you in advance.

M2E