Note to the next guy:

You don't need the register if there's only the ADC channel inside it (I keep the list only as documentation for the channel numbers).

Code:
'ADPCH = %00000000                   ' ADC POSITIVE CHANNEL SELECTION REGISTER
'   bit 7-6 Unimplemented: Read as ‘0’
'   bit 5-0 ADPCH<5:0>: ADC Positive Input Channel Selection bits
'               111111 = Fixed Voltage Reference (FVR)
'               111110 = DAC1 output
'               111101 = Temperature Indicator
'               111100 = AVSS (Analog Ground)
'               111011 = Reserved. No channel connected.
'               •
'               •
'               •
'               100010 = ANE2       * 16F18877 only
'               100001 = ANE1       * 16F18877 only
'               100000 = ANE0       * 16F18877 only
'               011111 = AND7       * 16F18877 only
'               011110 = AND6       * 16F18877 only
'               011101 = AND5       * 16F18877 only
'               011100 = AND4       * 16F18877 only
'               011011 = AND3       * 16F18877 only
'     26 --->   011010 = AND2       * 16F18877 only
'     25 --->   011001 = AND1       * 16F18877 only
'               011000 = AND0       * 16F18877 only
'               010111 = ANC7
'               010110 = ANC6
'               010101 = ANC5
'               010100 = ANC4
'               010011 = ANC3
'               010010 = ANC2
'               010001 = ANC1
'               010000 = ANC0
'               001111 = ANB7
'               001110 = ANB6
'               001101 = ANB5
'               001100 = ANB4
'               001011 = ANB3
'               001010 = ANB2
'               001001 = ANB1
'               001000 = ANB0
'               000111 = ANA7
'               000110 = ANA6
'               000101 = ANA5
'               000100 = ANA4
'               000011 = ANA3
'               000010 = ANA2
'               000001 = ANA1
'               000000 = ANA0

You only need to declare the channel in the ADCIN command:

Code:
        ADCIN 26, ADCinput