How to prevent cell from advancing to next row in DGV

I have a DataGridView that requires numeric input or just pressing the enter key with no value for 1 Column. I need to validate the input and am trying to use the CellValidating Event but having issues with it. I'm trying to display a popup message if the input is non-numeric and then have the cursor stay in the same cell and be highlighted. Does anyone have a code snippet that shows how to do this?

Thanks,