Target Days Suply in Planning book

Hi,

I have requirement to enter difernet TDS for different periods in planning book.

FOr this purpose i have chosen 1 in Product master for Target stock level method.

I have also deactiavted the macro for calculating the TDS from location product master.

Now it allows me to enter the TDS in planning book but when i save it it disaapears.

Can you let me know how to solve this issue.

Thanks

R