Hola, a ver si te sirve esto:
Código Delphi
[-]
function Buscar(const S1, S2: string): string;
var
I, J: Integer;
STemp: string;
begin
Result := '';
for I := 1 to Length(S1) do
begin
for J := 1 to Length(S2) do
begin
if (S1[i] = S2[J]) then
begin
STemp := UpperCase(S1[i]);
Break;
end
else
STemp := S1[i];
end;
Result := Result + STemp;
end;
end;