django forms in admin

[dummyman dummyman]

Hi , 

I ve a set of fields which is displayed in admin using fieldsets in django. But i want to modify the display of only one field. ie i used CommaSeparatedField , i want that 2 display in forms.MultipleChoiceField . How do i achieve it ? 

i did like this

class A(forms.ModelForm):

    fielda = forms.MultipleChoiceField....

    

    class Meta:

     model=A

then in admin.py

class Some(admin,ModelAdmin):

form=A

#fielsets

fieldsets = [ 

...

]

but im getting errors coz all the fields need to be displayed in forms .