Allow To Accept Null In Datagrid In VB And Save Last Entered Value In The Grid?

I'm writing a windows forms project in Visual Studio 2008 - VB, data are stored in SQL database.- I have a date field within Datagrid that could be Null or have a date in it. I had set it to show <none> when it's Null (Null is allowed for this field). The problem that I got is when user would need to delete the date from that date cell within the grid. I'm getting an error immediately after pressing "Delete" to clear the cell value. I had put in a work around - added the code for grid DataError event and assigned DBNull.Value to that cell and user is able to type in <none> for that cell or just press save, but it won't allow to go to the next cell in the grid if you don't save or type <none>. I'm sure that there is a better way handlig situation like that. May be using different event? I wasn't able to find anything else on it.- the other issue in the datagrid - if user fills in 3 cells out of 5 for example and press save while in the 3d cell - it won't save the value in the 3d cell. I also put a work around to check for the values in specific cells before saving but the problem with it - few cells could be Null (and should be Null). I can't check every single cell value and force user to type something in it.