Some observations from a remote toadstool...I was doing some testing on fields and things and ran across some apparent oddities (odd to me at least). The field was set to 'Number' type:
If the field is empty (null, whatever), it still evaluates to zero (i.e. field = 0? YES ). It doesn't seem like it should do this, i.e. NULL ≠ 0.
You can add multiple lines to the field IF you are using a checkbox set. So, create a checkbox set with value list "0¶1", check them both and the data in the field is "0¶1". Now, I can't TYPE that data into the field (if it were a plain edit box - I can't hit 'return' and get a CR that is; I can hit option-7 to get a pillcrow).
Oh, just noticed, too, that if you type in some data in an edit box that data will remain there when using checkbox sets. I guess this makes sense, but still seems a bit odd: checkboxes just add remove the given value from the field, regardless of what is there. Radio buttons properly obliterate existing values, of course.
More noticing: if using a checkbox set a "0¶1" DOES equal 1, but "1¶0" does NOT. Whilst the opposite is NOT the case: ""0¶1" does NOT equal 0, NOR does "1¶0" equal 0. (Pillcrows here are used to represent a carriage return, char(13), NOT the actual pillcrow character, char(182). A CR/char(13) is what you get when using checkboxes.)