Dear Farhad,

Your answer is good but incomplete.

Dear Vijay,

Your answer is taken from http://www.codeproject.com/KB/grid/DataGridViewMaskedText.aspx
Actually, I use the JThomas.Controls. I think is a good solution. For C#2.0

But lastly there is a better idea: http://www.codeproject.com/KB/MFC/UltimateGrid.aspx

I hope it can be useful for you,
ear