Chaim
The AVG function does not exist in the context that you are trying to use. You can use it if for instance you want the average off all the A column in you cursor, with either one of the following:

? calculate( avg( mycursor.a ) )
average mycursor.a to myAverage

In order to do what you want to achieve, you can manually calculate the average. Also, there is no need for a scan...endscan, use VFP scopes instead, as in

select MyCursor
replace all MyCursor.C with ( MyCursor.a + MyCursor.b ) / 2

HTH
Jaime

>I have a cursor with three columns.
>The third column (read only) is the avarage (a,b)
>the following command not working:
>

select mycursor
>scan
>replace mycursor.c with (avg(mycursor.a,mycursor.b)) in mycursor
>endscan

>What can I do?