Problem in using a Mating Assembly Macro

Hi all

I was using this post :

http://www.eng-tips.com/viewthread.cfm?qid=175155

to do some matings in Assembley , but whether I open a part or assembly I get a run time error 91 : Object variable or with block variable not set

I don't know in which line the set is not compatible with my assy, but I have chosen one of the components first ,only that I opened as Assembly that the parts already have a mating

is this a problem ?