Complicated Duplicate Issue

Hi

This is tricky, but I hope there is a way of doing this

I will simplify the problem to help.

I have 2 columns, A and B
A is ID1
B is ID2

How can I work out if there are duplicate ID2s pointing at the same LE ID without doing filters, so basically if there are more than 1 ID2s pointing to 1 ID1?

Another spanner is the works is that an ID1 can have more than 1 ID2.

Mini file attached which should help with my explanation

Kind regards

Keith