Add the field from the start

SELECT field1,fields2......,space(4) as age into cursor smf2 readwrite

>I created a cursor in my application.
>as follow: SELECT field1,fields2...... into cursor smf2 readwrite
>
>before running a report on this cursor I wanted to add some fields which I couldnt add them at the begining.
>
>so I did:
>m_alias="SMF2"
>
>when the following code executes:
>ALTER TABLE DBF(m_alias) ADD COLUMN age c(4)
>
>I get the following error
>Structural .CDX file is not found.
>
>after that I dont find the smf2 cursor in the data session anymore.
>
>what am I doing wrong?
>any help please