I'm testing out a data entry form and trying to put in a few simple rules to ensure that the appropriate fields are filled in prior to the user moving foward.  

I have a check box "Initial Review Complete" that I've attached 3 validation rules.  If any of the rules faile, the check box should be disabled (would prefer to un-check the box if marked but thats another topic!)  I can't get any of the 3 to work as intended (testing one at a time). 

Any suggestions would be appreciated.  I tried to follow the syntax found online for these rules, but I cant get the drop-down or text field to work right, and I couldnt find an example for the person field. 

All three rules are applied to the "Initial Review Complete" field.  When I enable them, they all disable the "Initial Review Complete" checkbox regardless of the values entered into the tested fields.

1) length(trim(mytextfield)) != 15

2) isNullOrEmpty(SPPersonField(Display Name))

3) SPDropDownField=='Please select a value...'