Possible to write DateAdd output to a cell VBA Macro?

All,

I have an issue with a macro where I'm trying to populate a cell with the results of a DateAdd formula.

This is a monthly report that is ran the 1st of each month.

I'm trying to specify a range to get the Max() of the existing dates for column I and then use the DateAdd to advance it one month. I've attached sample data and the corresponding macro. I'm not sure I'm getting the "rng" populated correctly.

Thanks for any help you can provide.

Brian