my graphicbutton repeat last command

Hi,
i have a Graphic Button ,
it's Beggining ok but if I'm doing what in autocad and then click the button again, repeated  last command.
Event invoke 1

(Button read a Combobox value (no Event - Event invoke 0) , 2 TextBox  value (no Event - Event invoke 0) and a chcekbox  value (clicked - Event invoke 1)

where i make error?

I found it, when I write in this art no error then


 
;;;(command "_.color" "_bylayer" "")            -------------- repeat last command

(setvar 'CECOLOR "bylayer") ----------------------------------no error

It's not clear from your reply whether you noticed the extra "" in your (command) call. In any case, (setvar) is better.