>I am not looking whether a certain property exist or not, I am looking if an object of a certain type (like a text box for example) is present in the form. I looked at PEMSTATUS(), but I'm not sure that really is the function I need...

If what you're looking for is a particular object, you could use PEMSTATUS() to see if the property containing the object exists, or you could use TYPE() to see if it's of type "O".

IF PEMSTATUS(_SCREEN.ActiveForm,"cntxxxxxx"),5)
  *
  * Object exists
  *
ENDIF

or

IF TYPE("_SCREEN.ActiveForm.cntxxxxx")="O"
  *
  * Object exists
  *
ENDIF

You could also spin through the form's Controls collection to see if what you're looking for exist. You may have to deal with containership heiarchy if the form is not the parent.