APD error when using customer exit variable in query

Hi guyz,

Just want to ask how can I resolve my error below in APD when extracting QUERY to CSV? The error occurs if I use a customer exit variable in the query I am extracting..But if I remove the customer exit variable and replace it with any filter or manual input variable the APD is working fine..

I am using customer exit variable since I need to run this APD every 1st day of the month and it must extract the data of previous month..Any other way to achieve this without using customer exit variable? Or how can I fix this error?

Thank you..

Loed