You need to create a search help with custom data selection by defining a search help exit. To do custom data selection, first, go to the “Definition” tab of search help, remove all the content of “Selection method” input and now input the new function module in the “Search help exit”. The signature of the new module should be same as the F4IF_SHLP_EXIT_EXAMPLE. To do this, you can look into the documentation inside F4IF_SHLP_EXIT_EXAMPLE. Now the data from the second system can be fetched with the help of remote function call.