How to create a formula that will concatenate the all (reference) of (specific supplier

Hi guys can you help me below:

I want to create formula that will automatically concatenate the references (references will be place in entire column (ex. D:D)) of one Supplier into one cell (ex. CE4)?

Concatenate function is good but it is inconvenient to work on it if I have 1000 individual products.
"If possible" I want excel formula not VBA

Example: All references are in (sheet1) Supplier name in cell (K4) will concatenate all reference in cell (M4)

I attached here before and after what I want:

sample 1.xlsx

Thank you so much JBeaucaire. It works fine and well.

How to mark as SOLVED?

Thanks,

Reimar