ya lo encontre:
void __fastcall Tdeposi::DBGrid1DrawColumnCell(TObject *Sender,
const TRect &Rect, int DataCol, TColumn *Column,
TGridDrawState State)
{
DBGrid1->Columns->Items[0]->ReadOnly = true;
DBGrid1->Columns->Items[1]->ReadOnly = true;
DBGrid1->Columns->Items[2]->ReadOnly = true;
DBGrid1->Columns->Items[3]->ReadOnly = true;
DBGrid1->Columns->Items[4]->ReadOnly = true;
DBGrid1->Columns->Items[5]->ReadOnly = true;
}
otra duda: como cambio el color de la letra de la celda que estoy editando.