Is it possible to merge data from unique subjects from multiple datasets into one file?

I have five datasets, one with subject demographic information, one with baseline outcome data, and then three with followup outcome data. All datasets have different numbers of subjects, and in some cases the same subject has multiple data. Is it possible to isolate the subjects that have data at each time point and put them (and their data) in a separate file?

I know it sounds complicated... but I appreciate any help.

[Jan]

Of course this is possible. Please explain, what a "dataset" is exactly, then a more precise answer is possible.

[Nathan Hogaboom]

Hi Jan, thanks for the response. By dataset I mean an MxN excel file with a bunch of datapoints. The first file is 558x12 (subject demographic information), and the 2nd, 3rd, 4th, and 5th are Mx14 (outcome measures). Each row has a subject's data both text and numbers.