Look at last pasted cell and if the same give me an error message box

I have made a macro that copies dates from 1 sheet and pastes them to another sheet. I do this everyday, with the dates changing. Right now I have it to look from bottom of the sheet up to the next blank cell and pastes the current dates. I want it to look at the last pasted cell and if the date is the same give me a message box error. Hope this makes sense.

Thanks
Jeremy