It might depend on the model, but LG should support IR key emulation commands in the form "[m][c][ ][Set ID][ ][Data][ ][Cr]" where Data is the IR hex code for your particular function (should be a table for these in the manual).

Volume Up would be "mc 00 02 \r" and volume down would be "mc 00 03 \r" (in a Crestron world) for 32LX1D.