Event when Excel window is activated

I'm trying to copy data from one program to excel. To save time I want excel to do all the pasting for me.

So, I have one excel workbook open and MS Dynamic NAV open.

I copy the data from NAV and then when I switch to the excel workbook I want it to paste the data in itself.

I've written the code to paste the data in. That works fine, however I can't get this code to fire when I activate or switch to the excel window. I've tried the following but it won't work

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And the following as well,

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Any thoughts?

But am I not activating the application or workbook or something like that....

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Would this work? Don't really know where to put it....