Check ?micontrol = .null. to see what is going on with NULL. Use isnull() function instead

IF ISNULL(micontrol)

>Maybe it´s a silly question, but I´m having some trouble to validate a NULL value. I´m taking data from a Excel Worksheet, don´t knowing how large is it. So, I need to break my DO WHILE when the program finds a blank cell. My code is something like this.
>
>

>	DO WHILE .T.
>		micontrol = .cells(lnfila,2).VALUE
>		IF micontrol = .null. then
>			EXIT
>		ENDIF
>                *....
>                *Some code that works fine...
>                *....
>        ENDDO
>

>
>Everything works fine, but I never can reach EXIT, and the other code continue excuting, logically sending me an error. Using the debugger, the value for micontrol is .NULL.
>
>What's wrong??
>
>Thanks in advance!