XLSApp is middleware software between Excel and your Client (Multicharts, Metatrader etc). Your Client is using DLL to access XLSApp and XLSApp is coordinating the communication between Clients and Excel. XLSApp is designed to run on your computer with low resource needs. You should run XLSApp before you call XLSgate functions. Moreover XLSApp is designed to be a debug instance for you. XLSApp will show you debug informations, such as Warnings, Errors.