Lookup function in load rules

Hello.

I have a question about using the lookup function in load rules.

My workbook is designed to be built for one single buying period. I would like to update it to include some measures that show data for the previous buying period. I created a mapping measure - to link each buying period to the next. And added lookup rules in the load rule group.

My map measure is setup similar to the Like-Item setup. (See first screen shot below).

I get an error. See second screen shot below.

Instead - If I add databases to these measures, and execute them in batch - and use the typical meas=meas.master rule in load-rule group, I am able to see data in the workbook.