VBA error with auto fill of user defined formula

I'm using a user defined formula I got from another post, concatall, that combines all text in a range. That formula works great, but I'm now attempting to use auto-fill in VBA to fill in this formula in a column. It works outside of VBA, but when the vba code runs, it fills the formula in all the cells with a result of #VALUE!. If I manually click on each cell or manually complete the auto fill, they work. Any idea what I'm missing? Appreciate any help, thanks!

I actually found my own answer in another thread, but wanted to post in case any one else comes across this issue, the function had to be set as volatile to update...

Application.Volatile True