>>What's wrong with 'modify class' ?
>
>I don´t need modify the class, only need know what library and class a selected the user.
>
>José Luis.

I see. I don't know a direct command/dialog. For a similar necessity I did my own. Class file part is regular getfile. To get class names into a listbox I used (while stripping code I might have made a typo) :

Select Reserved3  ;
 FROM ('_ClassFile_') ;
 WHERE LOWER(ObjName) == lcClassName AND LOWER(Reserved1) == 'class' ;
 INTO Array arrPEM
Use In ('_ClassFile_')
IF _Tally > 0
 lnLines=ALINES(arrPEMs,arrPem)
 ASORT(arrPEMs)
 WITH thisform.lstClasses
   .ListIndex = 0
   .Clear()
   FOR ix=1 TO lnLines
	IF ISALPHA(arrPEMs[ix]) && ByPass protected,hidden and methods
 	  lcItem = IIF(OCCURS(' ',arrPEMs[ix])>0, ;
        	LEFT(arrPEMs[ix],AT(' ',arrPEMs[ix])-1), arrPEMs[ix]) 
		.lstClasses.AddItem(lcItem)
	endif
   ENDFOR
ENDWITH

Cetin