You have just described how MetaTrader works and all the features that it has with its programming language MQL! There is no need for external applications as it already automates and runs scripts/EA's written in MQL. It can also extend functionality via Windows DLL libraries.
So, it seems that you have never used MetaTrader before, so I have to ask - what trading platform are you
currently familiar with or what are you currently using for your
PS! You can also use Inter-process communication in order to communicate, synchronize or exchange messages or data with other applications whether on the same machine or via networking. However, that all depends on your software development skills.
Like I have already stated - You do not need an external app!
You can accomplish all that you have described, from within MetaTrader itself, running a standard MQL EA (with a compact UI, with buttons, etc.). The same EA, can also do analysis and publish statistics or anything else that you may desire. MQL is a full pledged compiled programming language and even when there is something that is technically too sophisticated, it can be extended by using DLL library files.
All of this is really dependent on how good the software developer is and not so much about what MetaTrader/MQL is capable of. For a beginner or novice coder, like yourself, it is probably beyond your abilities (even with help).
So, you should really consider hiring someone that is capable of doing it for you and for a cost that is agreeable for you.
EDIT: PS! Obviously, if you insist on an external interface (webpage for remote control, etc.), then that can be accomplish too. It is really not a technical limitation, but it is just a question of how good the developer is.