How to test if a field does not contain anything else than returns or tab ?

[Andre.Bisseret]

Bonjour,

I need to test if a given list field in a stack contains some values  
or if it is empty.
Well, by "empty" I mean that the field contains not any word or  
number. But it happens that it may include carriage returns and/or tabs.
In such cases :
field "thisField" is empty
return false.

If there were only carriage returns, I could test if each line of the  
field is empty;
indeed :
line x of fld "thisField" is empty
returns true if the only character in the line is cr
but returns false if there is at least one tab in the line.

I just tried :
if last char of fld "thisField" is empty  ;-))

that seems working well ! but a bit strange and might be not reliable ?

Is there a better trick ?

Thanks for any idea

Best regards from Grenoble
André