ActionScript 2.0 :: Flash Portfolio - TellTarget Value Of Variable

I am working on a portfolio in flash which dynamically defines the target of the buttons. When a button is click an external swf is loaded, and the button sends the value of a variable to the loaded swf. So far I got it to work as I want it to, BUT the ouput-panel keeps giving the message:
Target not found: Target="this._parent.project" Base="_level0.button_1"

I am using this code:
on (release) {
this._parent.project.loadMovie("project.swf");
tellTarget ("this._parent.project") {
pnumber = a;
}}

The "pnumber" var is used in de project.swf to define a folder. "a" is a var with a numeric value. I know the tellTarget is an old-fashioned way of scripting, but so far it is the only piece of script that actually does what I want it to do (except for the error-message)
I tried:

Code:
on (release) {
this._parent.project.loadMovie("project.swf");
this._parent.project.pnumber = a;
}
But this resulted in an undefined var in my target clip, while the tellTarget did return the value for 'a'/'pnumber'.