Macro triggered by cell entry

[kappa0815]

Dear all,

I have a list with many columns and many rows.
Most entries are optional, but some are mandatory when an optional cell has been entered in the same row (with text)
So, the example:
cell c2 is optional, but in cell D2 a comment must be be added as soon as I put in text in cell C2

The same for D3, D4 and so on when C3, C4 have been entered and filled with text

at a minimum a warning pops up to enter a comment in the cell next to cell in column C

I do not want to add a button to start the macro. It should happen automatically.

Thanks for your help in advance.

Cheers,
Claus