How to get checked values from datagridview to a single textbox in C# windows application?

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C#

C#4.0

In my telerik datagridview first column is a list of checkboxes,when i am checked on that checkbox then i want to get the specific value of that checked row in to single textbox.And when i will uncheck that checkbox then the value of that checkbox row is deselect from textbox..........
How to do this......thank u....