Document preset & New document - Illustrator - Applescript

Hi !

Here is the problem i would like to resolve with appelscript.
I want to make a new file with units (millimeters)

I know i need to make a preset before making a new document ; but i don't know how to do !

Here is a part of the code i tried to do :

tellapplication "Adobe Illustrator"

activate

setdocument unitsofdocument presettomillimeters

makenewdocumentwith properties {width:297, height:210}

endtell

Thanks for your help !