Update All The Rows In A Single Column?

I can't seem to figure out how to update a single column for every row in my database...

con.Open()
Dim cmd As OleDbCommand
cmd.Connection = con

[code]....

What I'm looking to do is to update add a value to the given value already in the row. for instance:

id name value
1 peter 8
2 paul 10
3 mary 16.25

I just want to add a specific value to each row, such as "8"

id name value
1 peter 16
2 paul 18
3 mary 24.25