Create n tiles based on percent ranges rather than on count

*Title (this is from SPSS AnswerNet):
Creating n-tiles based on percent ranges, and not count of cases 
Description:
Q 
I want to split my data into n-tiles (in this case quintiles) 
where the group ranges are equal rather than the number of cases 
within each group; the aggregation is based on equal ranges and not 
equal counts. How can I do this? 
A. 
*The following sample job will do what you want. The crux of the 
job rests with computing variable to compute a cumulative total using 
the LEAVE command, and then a DO IF/END IF procedure to specify the 
grouping. 
*****. 
INPUT PROGRAM. 
LOOP #I = 1 TO 100. 
COMPUTE salesvol = TRUNC(UNIFORM(100000)) + 1 . 
END CASE. 
END LOOP. 
END FILE. 
END INPUT PROGRAM. 
COMPUTE cust_id = $casenum. 
EXE. 
COMPUTE dummy = 1. 
EXE. 
AGGREGATE /OUTFILE='AGGR.SAV' 
/BREAK=dummy 
/totl_vol = SUM(salesvol). 
MATCH FILES /FILE=* 
/TABLE='Aggr.sav' 
/BY dummy. 
EXE. 
SORT CASES BY 
salesvol (A) . 
COMPUTE cm_sale = cm_sale + salesvol. 
LEAVE cm_sale. 
FORMATS salesvol totl_vol cm_sale (DOLLAR8). 
EXE. 
DO IF (cm_sale < (.2 * totl_vol)). 
COMPUTE quintile = 5. 
ELSE IF (cm_sale >= (.2 * totl_vol) AND cm_sale < (.4 * totl_vol)). 
COMPUTE quintile = 4. 
ELSE IF (cm_sale >= (.4 * totl_vol) AND cm_sale < (.6 * totl_vol)). 
COMPUTE quintile = 3. 
ELSE IF (cm_sale >= (.6 * totl_vol) AND cm_sale < (.8 * totl_vol)). 
COMPUTE quintile = 2. 
ELSE IF (cm_sale >= (.8 * totl_vol)). 
COMPUTE quintile = 1. 
END IF. 
EXE.