Welcome to the Forums.
I've branched your question to a new thread.
Could you please share your packaged workbook (*.twbx file)?
If your data is sensitive, would you like to demonstrate
base on a Superstore dataset?
I'm glad to help.
If i understood it correctly, you are trying to replace Null values with '0'. Try IF NULL in calculation.
Thanks for your replies so far. The original data I have is proprietary and so I cant post the workbook. Let me mock up the data from Superstore over the weekend and post it. Will appreciate if you can weigh in then as well,
Try change your value expression like this: IFNULL( [Last Value],0 )