>Step1)User inputs the data in the grid(table is invdetail)
>step2)press save 'button',press 'print' button (there will call external prg to do some calculation
>step3)the report is printed correctly
>step4)user press "new" button again,
>There is an error prompt "ThisFormSet can be only used withthin a method"
>if i press "ignore", another error is prompt"Alias 'invdetail' is not found.
>
>That table 'invdetail' is put in the dataenvironment (buffermode is 5)
>Pls help, Everytime the user "new" the invoice, everthing the error is prompt.
>
>Thanks in advance

I suggest you correct the first error first - the second error is likely to be the result of the first error.

Pressumably, you used a reference to ThisFormset, outside of a method code (of the Formset), for instance, in one of your functions. I suggest you use the debugger, to find out where you used this reference.