VS 2010 disable button column's cell

Hi

I have four columns

col1 - gridveiwcol
col2 - gridveiwcol
col3 - gridveiwcol
col4 - buttoncol

based on the col1's value im disabling or enabling the remaining columns. It works fine for col2,col3 if we disable using READONLY = TRUE property.
But the button column is not working if i give "dgvSCRNFLD.Rows(rowindx).Cells("col4").ReadOnly = True".. kindlty help me on how to disable the button cell..\

Thanks
in advance