>Thanks Fabio I'll keep that in Mind, May be I need to switch from
>ROUND(numb,2)
>
>To STR(numb1,19,2) = STR(numb2,19,2)

This don't change the issue,
STR uses round for compute the decimals part:

#DEFINE 	_DECIMALS 		5
#DEFINE		_ERRORPOWER		8
#DEFINE		_CICLES			50000

CLEAR
? "Expected fails:",INT(10^(_DECIMALS-_ERRORPOWER)/4*_CICLES)
t=0
FOR K=1 TO _CICLES
	X=RAND()*1000
    E=(RAND()-0.5)*1E-_ERRORPOWER
    IF ROUND(m.x,_DECIMALS) # ROUND(m.x+m.E,_DECIMALS)
      t=t+1
    ENDIF 
NEXT
?? "     fails: ",T

? "Expected fails:",INT(10^(_DECIMALS-_ERRORPOWER)/4*_CICLES)
t=0
FOR K=1 TO _CICLES
	X=RAND()*1000
    E=(RAND()-0.5)*1E-_ERRORPOWER
    IF STR(m.x,18,_DECIMALS) # STR(m.x+m.E,18,_DECIMALS)
      t=t+1
    ENDIF 
NEXT
?? "     fails: ",T

Another point, 19 in STR() is useless,
18 is sufficient ( 15,95 digits are used )

STR cannot to be used with a unbound currency:

x=$99999999999999.9900
? x,STR(x,19,2)

Fabio