Need help adjusting VB macro for appending data to rows with matching index numbers

Thank you so much, the code is working now, although it's adding blank columns between each group but that is something I can easily fix.

I would really like to know how it works, so that if I need to make changes, I can do so without having to bother all of you. For example, right now there are seven columns of data from A to G that will be the same for each mouse- what would I need to change if I had 6 columns of data instead?

As always, your quick response was a lifesaver!

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I do not know your knowledge of dictionary object.

If Not .exists(aNum(indx, 3)) Then
test for the existence of key for each column C rows, so it is testing column C for duplicates.
If there are duplicates ,the code then goes in to this line
Else section
It then append column 8 to last column

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I have change the above line in to

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This is more flexible as you can see that if there is a duplicate, i.e. if the key exists, then it goes in to else section. In the else section, you can see column 8 to last column is included. You can change to what ever column you want.
UBound(aNum, 2)) indicates the upper bound(The last column). You can also change this in to fixed column

AB33, thank you very, very much! I really appreciate it!