I am starting to like the 18F4320, made my head hurt at first.
I am working on a pyrometer with a K type thermo-couple and a LM34 for a reference. Have not looked at the data sheet for the PIC you are using, may or may not be close to the 4320. If it is, here is the pyrometer code so far, might give you some ideas.
Code:
 DEFINE OSC 8
   OSCCON=%01111000

DEFINE LCD_DREG     PORTC
define LCD_DBIT     0
DEFINE LCD_RSREG    PORTD
DEFINE LCD_RSBIT    1
DEFINE LCD_EREG     PORTD
DEFINE LCD_EBIT     0
DEFINE LCD_BITS     4
DEFINE LCD_LINES    2
DEFINE LCD_COMMANDUS    2000
DEFINE LCD_DATAUS   50

ADCON1= %00011011  

temp1        var byte
temp2        var byte
T1	       var byte
T2             var byte

TC	VAR    WORD
TCT    VAR    WORD
TX	VAR    WORD
TXI	VAR WORD
TXIU	VAR WORD

RUN:
	HIGH PORTD.2
	PAUSE 100
	LOW PORTD.2
	PAUSE 100
        gosub getT1
        GOSUB getT2
        T1 = temp1
        LCDOUT $FE,1,"LM34 ",#T1
        lcdout $FE,$C0,"TC ",#TXIU
        GOSUB D_INDEX
	GOTO RUN

getT1:
	ADCON0= %00000001  
        ADCON2.7 = 0
	gosub getAD
	temp1 = ADRESH
	return
	
getT2:
	ADCON0= %00000101   
        ADCON2.7 = 1
	gosub getAD
	TC.highbyte = ADRESH
	TC.lowbyte = ADRESL
	return

getAD:
	pause 50
	ADCON0.1 = 1
	pause 50
	return

	END

D_INDEX:
TX = TC 
'STEPS
LOOKDOWN2 TX,>[898,895,892,889,886,883,879,876,873,870,867,863,860,857,854,850,_
847,844,841,838,835,832,828,825,822,819,815,812,809,805,802,799,795,792,788,785,_
782,778,775,772,769,765,762,758,755,751,748,744,741,737,734,731,727,724,721,717,_
713,710,706,703,699,696,692,689,685,682,678,675,671,667,664,660,656,653,650,646,_
643,639,635,632,628,624,620,617,614,610,606,603,599,595,592,588,584,580,577,573,_
570,566,562,558,555,551,547,544,540,536,532,529,525,521,517,513,509,506,502,498,_
495,491,487,483,479,475,471,468,464,460,456,453,449,445,441,437,433,429,426,422,_
418,414,410,406,402,398,395,391,387,383,379,375,371,367,363,360,356,352,348,344,_
340,336,332,328,324,321,317,313,309,305,301,297,293,290,286,282,278,274,270,267,_
263,259,255,252,248,244,240,236,232,229,224,221,217,213,209,206,202,198,194,190,_
187,183,180,176,173],TXI

'TEMPERATURES
LOOKUP2 TXI,[2500,2490,2480,2470,2460,2450,2440,2430,2420,2410,2400,2390,2380,2370,_
2360,2350,2340,2330,2320,2310,2300,2290,2280,2270,2260,2250,2240,2230,2220,2210,2200,_
2190,2180,2170,2160,2150,2140,2130,2120,2110,2100,2090,2080,2070,2060,2050,2040,2030,_
2020,2010,2000,1990,1980,1970,1960,1950,1940,1930,1920,1910,1900,1890,1880,1870,1860,_
1850,1840,1830,1820,1810,1800,1790,1780,1770,1760,1750,1740,1730,1720,1710,1700,1690,_
1680,1670,1660,1650,1640,1630,1620,1610,1600,1590,1580,1570,1560,1550,1540,1530,1520,_
1510,1500,1490,1480,1470,1460,1450,1440,1430,1420,1410,1400,1390,1380,1370,1360,1350,_
1340,1330,1320,1310,1300,1290,1280,1270,1260,1250,1240,1230,1220,1210,1200,1190,1180,_
1170,1160,1150,1140,1130,1120,1110,1100,1090,1080,1070,1060,1050,1040,1030,1020,1010,_
1000,990,980,970,960,950,940,930,920,910,900,890,880,870,860,850,840,830,820,810,800,_
790,780,770,760,750,740,730,720,710,700,690,680,670,660,650,640,630,620,610,600,590,_
580,570,560,550,540,530,520,510,_
500],TXIU

RETURN
As you can see I do not use ADCIN. I am a control freak