How to contour a group of objects?

[gaftalik]

Hello everyone,

In my attached example i need to make a white contour line on the exterior side of my grouped of hexagons (pattern).
First i tried to add lines but it also added lines to the interior hexagons the thing that i dont want, then i tried to use the contour tool but it made an altered contour and changed the interior cells too.

Any suggestion please?

Thank you for your help !

Gaf
Xara pro designer X11