>I need to change in runtime some of the captions of labels and/or commandbutton, due to certain preferences of users. It's near to change the caption when switching between languajes.

Are you using your custom label class?

If so, one of the ways to achieve what you want would be to define some property of your label class, say, cUsedLanguage.

Add Assign method to this property and put there code like

lparameters uNewVal
if not this.cUsedLanaguage == m.uNewVal
   this.cUsedLanguage = m.uNewVal
   this.ChangeLanguage(this.cUsedLanguage)
endif

Then, when you want to change language you may call thisform.SetAll("cUsedLanguage", "Spanish") and this would call your method.

That's a trick I learned ~7 years ago from Tray Walpole..