How to enter asset management fees?

[J. Perkins]

I have been busy entering all of my investment information into GnuCash 
1.8.1, and I've hit a case I can't figure out. My 401(k) charges an 
annual "asset management fee", which shows up on the statement as a sale 
of shares of each investment. I entered this into gc as a sale of 
shares, transferred to an expense account, and marked as a "fee". 
However, the advanced portfolio report shows this as "money out" and 
considers it a return on my investment, skewing my total return numbers. 
Am I doing this right? Is there a better way to enter these kinds of 
transactions that won't mess up the performance numbers?

Thanks!

Jason