Requested by Mr Ganesh Joshi, here is an update to allow negative Integers.
Hope it helps!

Storage and RAM gains with the PROGMEM keyword:

• v1.0.5: DoubleBarPot.ino uses 7446 bytes and 310 bytes of RAM
• v1.1.0: DoubleBarPot.ino uses 7538 bytes and 230 bytes of RAM

Comment out this line to revert the original behavior:

#define LCDPROGRESSBAR_USE_PROGMEM

Storage and RAM gains:

• v1.0.4: DoubleBarPot.ino uses 8036 bytes and 498 bytes of RAM
• v1.0.5: DoubleBarPot.ino uses 7446 bytes and 310 bytes of RAM

Yet to come: usage of PROGMEM

Adding shortcuts disableBar1() and disableBar2()
Remove a compilation warning

Added support to display 1 bar only
Example for showcase

Added example with trimmer potentiometers
Corected entry pin 2 as the schema on initial example