IF-ISTEXT-SEARCH, to return values from multiple cells

Hi,

I have a spreadsheet with two tabs. On the first tab is a list of event dates in column E and the groups invited to those events in column D. So it might say that an event on one date was attended by group1, group3, group7, while the row below shows an event on the following day attended by group3, group 4, group6. On the second tab is the full list of groups.

What I need is a formula on the second tab that will return all the dates attended by each group, either in one cell separated by commas or in consecutive cells in that row.

So far I've developed this formula for the second tab:
=IF(ISNUMBER(SEARCH($C2,'Tab1'!$D4)),'Tab1'!$E4,"")

The problem is that this just delivers the first date of attendance without also providing the later dates.

Any suggestions?

Attached is a mini-version that I made, with some of the non-essential data removed. Sample1.xlsx

The formula that I am working with is in cell B2 of the second tab. In my full length version of this spreadsheet the dates go through the entire year, and there are nearly 500 groups. I need a way to track that every group is being invited an equitable amount of times.

That didn't quite work. Maybe it was my fault, I didn't understand the "confirm with control+shift+enter" part. The dates in column B are incorrect, and the additional dates are not showing up in the other columns.
Sample2.xlsx

Got it! Now it works great! Thanks for all your help!