>On Rule Begin Pascal Script:

Begin
  psExitCode:= 1;
  // Init Var
  psVSA := '';
End.


> On Destination Pascal Script:

Var
  tmpFile1, tmpFile2: String;
Begin
  psExitCode:= 0;
  // ... add your code here
  tmpFile1 := psFilePath + psFileName;
  // _0 File
  If pos('_O', AnsiUpperCase(tmpFile1)) <> 0 Then
  Begin
    tmpFile2 := psStringReplace(tmpFile1, '_O', '_R');
    IF FileExists(tmpFile2) Then
    Begin
      If psVSA = '' Then
      Begin
        psVSA := tmpFile1;
        psExitCode := 1;
      End
      Else
        If SameText(tmpFile2, psVSA) Then
          psExitCode := 1;
    End
    Else
    Begin
      If SameText(tmpFile2, psVSA) Then
        psExitCode := 1;
    End;
  End;
  // _R File
  If pos('_R', AnsiUpperCase(tmpFile1)) <> 0 Then
  Begin
    tmpFile2 := psStringReplace(tmpFile1, '_R', '_O');
    IF FileExists(tmpFile2) Then
    Begin
      If psVSA = '' Then
      Begin
        psVSA := tmpFile1;
        psExitCode := 1;
      End
      Else
        If SameText(tmpFile2, psVSA) Then
          psExitCode := 1;
    End
    Else
    Begin
      If SameText(tmpFile2, psVSA) Then
        psExitCode := 1;
    End;
  End;
End.