1. The new column has to be an item comparable to the data in your second report you are pointing to. Use the expression editor in the Edit Definition to rename your column, then, use the filter to call that new column name "in" , "dataset", and a dialog box will come up asking you to choose an .imr and a column in that .imr. Once you choose a column, then click Open, you are back to viewing your filter and it should say "new column" in (DATASET). It is then that you will decide your join to the dataset with the report that you are using in order for it to work. Choose 'and', then Catalog Columns, and decide if anything in your report can join to your catalog so that the results make sense, then the '=' , then the matching item in your 2nd report.
2. This may not work in your situation. However, it is worth a try. You can only use data from the same catalog.