determine whether testexecute is running or testexecute

The correct way is to check BuiltIn.ParamStr(0) - it returns the test runner path (TestComplete path or TestExecute path).

WaitProcess("TestComplete") can theoretically cause a false positive if both TestComplete and TestExecute are running at the same time (as of v.11.20 they cannot, but it might change in the future).

var testrunner_path = BuiltIn.ParamStr(0); // Example: "C:\Program Files\...\TestComplete.exe"
var testrunner = aqFileSystem.GetFileNameWithoutExtension(testrunner_path);
switch (testrunner)
{
  case "TestComplete":
    // ...
    break;
  case "TestExecute":
    // ...
    break;
  default:
    // This shouldn't happen
    Log.Error("Unknown test runner: " + testrunner_path)
}

UPD: Here's another way that will work correctly:

var testrunner = Sys.FindId(Win32API.GetCurrentProcessId()).ProcessName;
// "TestComplete" or "TestExecute"