how to create a indexed transparent table ?

hi all,

my requirement is i have to create a indexed transparent table T1.

i.e.,field1---index#,

field2---xxxxx,

field3---xxxxx.

for 1st record, i have to have 1 in index#,..for nth record i should have n in index#.

for each record inserted in table t1, should i have to manually fill the index#.

else v have any option in SAP so that for every record, index# is generated by the system itself.plz help,its urgent.