Link data to an ID across multiple sheets

I am working on a research project that has many subjects and program attendance data across multiple sheets. There are several programs and they each last many weeks. We want to know how many times they attended a session, but there are too many to go through and count individually. Is there a way that I can link the data for that person to their ID number to calculate the total sessions attended? The issue that I am running into with this, is that I am not able to link up the data across multiple excel sheets.

Thanks for your help.

Thanks for your response. How would I go about doing the indirect function? I attached a sample of our data.

Can you provide an example of the result you'd like for a specific ID? It's not clear if each day counts as attendance. For example, what's the correct attendance for 54168?

Sure! So, for ID number 54168, they attended 15 sessions in the second program and 14 sessions in the third program. The total session count for ID number 54168 would then be 29. We are continually adding new sheets and so we do not want to have to go back and add the most recent total. If possible, we are looking for a way that the # of sessions attended would automatically update as we enter the data.

The dates do not have anything to do with the count. That is simply when the session took place.

Thanks!

Thank you for your response! I am not familiar with the process that you used. Would you be able to explain how you performed that procedure? Or could you direct me to some literature on the subject?

Thanks again!

Thank you!