Excel VBA Sum a column from closed workbooks into current workbook w/ macro

Hello Everyone,

I am new to VBA and really want to dive into learning this! I am looking into how I would create a macro using VBA to go into 4 closed workbooks and sum the same column (C:C) on the same worksheet (Trial Balance) for each differently named workbook and insert the sum of each column into cells A1, A2, A3, A4 on the current workbook w/ the macro. Can anyone please give guidance on how to accomplish this? Any help is greatly appreciated!

Thanks!