Greg
Unfortunately no, there is no way to manually lock a task if you are using
Project Standard. In the standard edition there is not way to allow
read/write access to your project while preventing users from viewing any
sensitive information or preventing them from performing any specific
functions.
Project Professional / Project Server has a feature that protects actual
progress data using mangaged periods. All actual progress is entered through
a timesheet. Entries are stored in protected fields which can be synchronised
with the plan if any manual adjustments have been made.
I hope this is of some help
--
Regards
Chris Marriott
UK - EPM Consultant & Trainer