how to change current culture of class library (dll)

Question

i have a dll that it have a form and this form support two language (with loacalizable,language property).

and after that i add our dll to the main project and call the form from dll. the language of the form still in the default mode.

I must say that I set the value of the CurrentCulture and CurrentUICulture in the program.cs as follows :

Thread.CurrentThread.CurrentCulture = new CultureInfo("ar-IQ"); 
Thread.CurrentThread.CurrentUICulture = new CultureInfo("ar-IQ");

Q: how i can change the defualt culture of the form from outside a dll or into dll but programically?

please anyone help me.

Thanks