coding help needed: set, increase and log review priority

[Julius Dittmar <Julius.Dittmar@gmx.de>]

Hi,

lisp is still a mystery to me, so I need help coding some functions I
would like to use.

What I want is a property 'ReviewPriority', which can take integer
values, and a property 'LastReview'. I need functions that

- increase ReviewPriority by one, assuming an initial 0 if there's no
value set, up to a hard-coded maximum of 5, set LastReview to the
current date, and log the change (new value and date are sufficient) in
the LOGBOOK drawer

- set ReviewPriority to a fixed value (for example 1), set LastReview to
the current date, and log the change in the LOGBOOK drawer

- set ReviewPriority to a user-given value (clipping to the acceptable
value range of 0 to 5 would be a boon, but is not necessary), set
LastReview to the current date, and log the change in the LOGBOOK drawer.

Additionally I'd like to bind the increase function to C-c r and the
function with user input to C-c R.

Any help welcome!

Thanks in advance,

Julius