//-----------------основное окно программы----------------------------------------------------------
__fastcall TForm_MainForm::TForm_MainForm(TComponent* Owner)
	: TForm(Owner)
{
}
//------------------функция---------------------------------------------------------
func_StringHeshMD5(const String Text)
{
String resMD5;
.....................
.....................
}
//---------------------------------------------------------------------------------------------

//-----------------------Вторая форма----------------------------------------------------
void __fastcall TForm_Avtorizacia::BB_enterClick(TObject *Sender)
{

	func_StringHeshMD5(E_UserPassw->Text);
}
//---------------------------------------------------------------------------

[bcc32 Error] Unit_FAutorizacia.cpp(69): E2268 Call to undefined function 'func_StringHeshMD5'
  Full parser context
    Unit_FAutorizacia.cpp(50): parsing: void _fastcall TForm_Avtorizacia::BB_enterClick(TObject *)