Can I use one fill code to fill comboboxes in multiple forms?

Hi, I'm new to Excel Forum and new to vba.

I love excel and want to take advantage of more of its capabilities. I am very unfamiliar with vba vocabulary but have managed, through the aid of several forum posts, to copy/paste and modify codes to work for my needs. I have recently learned about the idea of modules, this idea that I can continue to call the same operation into multiple modules/forms, rather than having the entire operation re-written in each module/form. That being said, I have several forms which re-use various comboboxes, and I currently have the whole fill code for each combobox written in each form's code, and was wondering about the possibility of writing a fill code by itself, and then calling it to a form code. For two reasons:To make the form code look cleaner, and so that if an adjustment has to be made I don't I have to make it in every form's code.

Thanks for your help!

Somehow I seem to be making it more complicated than necessary, I have attached a simple spreadsheet with two buttons, "Easy" and "Learning". The "Easy" button opens a form with a combobox filled the redundant way which I know how. The "Learning" button ought to open a similar form, but with the combobox filled using the new (new to me anyway) sub method. I continue to get "Run-time error '424': Object required". If you guys could take a look at this and teach me the error of my ways that would be great. I'm afraid I'm going to embarrass myself with something terribly simple.

Thanks so much!

ComboBoxFill.xlsm