There is no way to do this with the current compucorder software as the same offset will apply to all values collected.

Adding a dc bias to analog value to the signal will probably work
You could use a rail-to-rail opamp and add a dc bias using a summing circuit, something like this.
build circuit on breadboard and put in project box to make it reliable.
You can pick up the 5V supply from the usb port from the vc and gnd connections
If you want a smaller supply voltage value you could use a dc dac output will supply up to 20ma of current at any voltage up to vc.