I have code to put a checkbox in a column. The column is data-bound to a cursor column/field. However, at runtime, I cannot change the value. Anyone aware of what might be doing wrong?

*!* Threshold Checkbox Column
to_grd.AddColumn(to_grd.ColumnCount + 1) && l_is_lt_threshold
lo_col = to_grd.Columns(to_grd.ColumnCount)
lo_col.ControlSource = ALLTRIM(tc_alias) + ".l_is_lt_threshold"
lo_col.AddObject('chk_threshold', 'chk_dataqc_grid')
lo_col.CurrentControl = 'chk_threshold'
lo_chk = lo_col.chk_threshold
lo_chk.Caption = ""
lo_chk.Width = 25
lo_chk.ToolTipText = 'Less than threshold QL'
lo_chk.SpecialEffect = 1
*lo_col.Sparse = (( .F. ))
lo_col.RemoveObject("Header1") && Standard header does not apply
lo_col.AddObject("Header1", "hdr_dataqc") && Put in what we need
lo_hdr = lo_col.Header1
lo_hdr.Caption = '< Threshold'
lo_hdr.Alignment = 6
lo_hdr.ToolTipText = 'Less than threshold QL'
lo_hdr.l_static_picture = (( .t. )) && Do NOT change this picture on sorting
lo_col.Width = 40
lo_col.Alignment = 2