How to disable ability to change the data date, yet allow them to F9 the project

Yesterday one of the P6 users comes to my office and tells me P6 is all messed up. Specifically the CUR schedule is showing the wrong dates.

I open it, and sure enough the dates are really strange looking.  Things are statused ahead of the data date. I asked what she was doing when it happened.

She says "well, I saw that the data date was wrong, so, I changed it".

I take a look, and she has changed it to last months data date. When I asked why in the world she would change it to May month end, she says "well aren't we supposed to be statusing May right now?"