void __fastcall Tdm::qrDivisionIDGetText(TField *Sender, AnsiString &Text,
      bool DisplayText)
{
  // Так для поля TFieldInteger
  if(Sender->Value ==  1 ) Text =  "Ц" ;

  // Так для любого поля
  if(Sender->AsString ==  "Y" ) Text =  "Ц" ;
 или
  if(Sender->AsString ==  "True" ) Text =  "Ц" ;

  DisplayText = true;
 // В гриде увидешь галочку.
}
//---------------------------------------------------------------------------

if(DBGrid1->SelectedField == MyField){
  DataSet->Edit();
   if(MyField->Value ==  1 ) MyField->Value =  0 ;
   else MyField->Value =  1 ;
 или
   if(MyField->Value ==  "Y" ) MyField->Value =  "N" ;
   else MyField->Value =  "Y" ;
 или
   if(MyField->Value ==  "True" ) MyField->Value =  "False" ;
   else MyField->Value =  "True" ;
  DataSet->Post();
}