STOP LOOPING_table control

iam having following sytax....

in my pai module...

PROCESS AFTER INPUT.

LOOP AT ITAB.

CHAIN.

FIELD ITAB-filed1.

FIELD ITAB-field2.

FIELD ITAB-field3.

FIELD ITAB-SELKZ Module ON_SELECT on request.

endchain.

ENDLOOP.

MODULE LOAN_USER_COMMAND.

.....so in above coding... ithink you can under stand that SELKZ is for to selct the table control row.... so if you selct the table control row then it will go into the module followed by...SELKZ,

and here now iam modifiying above coding like this.....

PROCESS AFTER INPUT.

LOOP AT ITAB.

CHAIN.

FIELD ITAB-filed1.

FIELD ITAB-field2.

FIELD ITAB-field3.

FIELD ITAB-SELKZ.

endchain.

ENDLOOP.

Module ON_SELECT on request.

MODULE LOAN_USER_COMMAND.

.......it was also properly working but....the thing is...

in first coding the loop is partially running before gointo this module....but in second part the loop is completing....so because if this iam facing trouble inthe caluculation part which is in that module and linked with the entries of the field1 and filed2....

so now my quetio is...

i want to stop that...

loop in second..... one when one perticuler value is met.....but if i write if condition,...it was showing error like...if is not defined....

please answer...

Thank you,

Naveen.....