SAP Message TT052 - A maximum of 999 repetitions are allowed

Diagnosis
A DO statement allows a maximum of 999 loop passes. You entered avalue greater than 999.

Procedure
Reduce this value. If you need more than 999 loop passes, you mustnest several DO statements.

Example for 1000 repetitions:
DO 100
DO 10
[Statements]
ENDDO
ENDDO