Want to simplify my Macro

Hi,
I'm not an expert in VBA but I like to play around and learn by myself. Unfortunately, I can't always find the answers I seek just by going through Google :/
That's why i come here today.
I have a Macro that changes the two following columns of a modified cell on a D8:AY259 range. It works fine, but I feel like the way I wrote it is maybe not optimal. Can someone tell me if it could be improved? Also I would like to add to my code that when there is multiple selection "then Exit Sub" and the user press delete, that the two following columns clears out as well.
Thanks for your help!

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Here is some optimization:
With this you can start:

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Maybe you can help me now. To register on my webpage www.virtual-forms.com and become a beta tester of new concept of Excel Userforms and if you love it, maybe tell some friends about it :-)

Davor

For the selection you can try to play with Areas >>>>> Columns and Rows:

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