Combine data from multiple workbooks into one, while combining sheet data

Hi,

I have a problem in front of me that I'm not able to solve on my own or through Google. I'm hoping the fine folks here can give me some leads to pursue.

I have between 2 and 4 workbooks, each consisting of exactly four worksheets, that I need to combine into a single master workbook via user form. The problem is that I don't simply need to grab the worksheets and append them to the master workbook - instead, I need to grab the data from each and place it in the corresponding sheet of the master workbook.

In other words, I have books A, B, C, and D. Each of them have sheets 1, 2, 3, and 4. Master book is labeled M.

I need to grab A1, B1, C1, and D1 and place them in M2. A2, B2, C2, and D2 go in M3, and so on.

Also, I need the sheets to be selectable via userform, as the naming scheme won't always be predictable. If the solution is much simpler by grabbing files from a folder, I'd appreciate that answer - I can figure out how to make it operate from a userform-derived array later on.

Duplicate cells/rows are not an issue - some will be duplicate, and that is both anticipated and expected.

Is there anyone who might be able to help me with this at all? I'm not really sure how to approach this problem. I'm able to grab the sheets from a book, but that doesn't really help me all that much; the actual data needs to be appended, instead.

Thanks in advance for any replies or assistance. Please let me know if you need any more information from me, and I'll be glad to provide it.