How to automate a process in an external program?

I'm using an external program which features an input box where a wavelength can be typed and hence selected. I want to use MATLAB to automate this so that I can sweep through a series of different wavelengths at the push of a button over a given time period. I'd imagine it would make use of a Loop function.

The issue I'm having is how to import the external program into matlab. There's a range of .exe, .dll etc but none of them seem to work - I keep getting random symbols (look like the wingdings font). I'm rusty with MATLAB so it might be a command that has to be written to get the interface onto matlab to write a script for that process. Any help would be greatly appreciated.

[OCDER]

Got a lot of questions before we can provide a solution:

Does this external program accept trailing inputs?

for example:
ExtProg.exe -option a -option b

Does the user have to input a wavelength for every iteration?

ExtProg -> user input -> ExtProg -> user input -> ExtProg -> user input ?

Why do have to use Matlab and not a powershell script?

What does the external program do other than ask users for a wavelength via an input box? Matlab has it own input box function inputdlg.

What is the output of this external program? Does it generate a file?