You need z/OS DFSORT V1R5 PTF UK90013 to use DATASORT. That PTF has been available since July, 2008. Ask your System Programmer to install it (it's free).
If you can't get it installed, then I need more information in order to help you:
Show an example of the records in your input file (relevant fields only) and what you expect for output. Explain the "rules" for getting from input to output. If the first record can be identified in some way (other than being the first record), say how (e.g. 'H' in position 1). If the last record can be identified in some way (other than being the last record), say how (e.g. 'T' in position 1). Give the RECFM and LRECL of the input file. Give the starting position, length and format of each relevant field.
It would also help if you show the job you tried to use and the //TOOLMSG and //DFSMSG messages you received.