variable not found comparing catalogs

[EQ12]

Hi everybody,
I'm a new user of zmap, and I would want to compare two catalogs to identify identical events, but when I try to do this a MatLab several errors occur: "variable a not found" "error using comp2cat>my_loadcatalog (line 350), files not contain the expected variable name"; "error in comp2cat: (line 17) nie=my_loadcatalogue('First')"; "error in ZmapMainWindow_catalogue_menu>@ etc" (line 73).
I have attached a screenshot of my pc below.
cat_a_b
What can I do?
Thank you very much, I will really appreciate any help.