VB 10: Copy from textbox to datagridview cells

I have a datagridview in my app in which two of the cells usually have the same data so I'd like to be able to enter the data just once.

Two options as I see it - but always happy to hear of others!

1. Text box on the form with a copy button - contents of text box copied to to the two cells.
2. Enter data into the first cell which is copied into the second cell. In this case, it would be possible to change cell 2s contents on the odd occasions when data differs.

The datagridview has a table binding source and data entered is always into a 'new' row.

Thanks