Error while confirmation of Order in Co11n?

Dear Expertise

I am using one exit for co11n.

CONFPP05

Now, In this I am using one validation  on BWART and RGEKZ(Backflush Indicator).

Now, when I run Co11n and enter the details, its working fine for my Error message which I have displayed if Backflush is null for Order No.

Now, when i press BACK or SAVE , it ask me with a POP UP "Do you want to save the confirmation"

I click on yes. It throws a dump as

Exception condition "DUPREC" triggered

I have already searched on this Dump but not able to sort out this issue.

Help me to sort out this issue gurus.

Thanks

karan