My solution will enable you to control that motor (change step rate, direction, # of step) from not only MAC but smartphone or PC via WiFi using any Web browser.
I will use ESP8266, a 32-bit MCU with WiFi connectivity capable, developing a small web server inside the MCU and expose Rest API for any web capable devices to control the motor. There will be also a small HTML/JS web page to you to control it. With Rest API support, you will develop the project more (not in this scope) such as controlling it from App.
Limitation: The MAC, Smartphone... must be in the local network. If you want to control it from anywhere via the Internet, a port forwarding on your router (and firewall if any) must be opened.
About hardware, beside ESP8266, a small driving module will be needed as well. Anyway, total hardware cost, include ESP8266 will be very cheap.
Scope and delivery: I am going to deliver the code for the esp8266, document and guide you to install on your system. Of course, during development, I will test it on my own hardware but there will be no hardware shipped. If you need to build a prototype and ship it to you, additional cost is required.
Please also notice that I am from Vietnam (UTC+7) so we will need to pick a timeslot for discussion - usually, your early morning or evening time will works.
Please do not hesitate to let me know if you have any question.