newby needs help with multiply selection input box

hi there all - complete newby and learning php by copying code from places like and trying to figure out why they dont work for me (or why they do when they do)
anyway - been looking for a data grid for a while and tried few - most do the job fine but in need some extra option that i could not get anywhere so heres hoping that this can do it
i have got this working following your very good examples but now i want to edit one of the fields in a very specific way - the field is called 'Keywords' (which is a string of keywords that describe that particular database record) - i want to have predefined keywords which i will be able to choose from as a box of multiply selection
let's say the databse is of songs and the predefined keywords could be rock, electronica, folk, warm, fast, slow, atmospheric etc. - i want o be able to choose in the grid one or more of these and that will update as a string with space between
hopefully i made myself clear :)
any ideas?

Maybe if i explain myself better i will get more responses :)

i guess if i was to give an example it will be like that
let's say there is a database record i want to update - it has 2 fields SongName and Keywords - the specific entry name is 'Song1' and the Keywords field is:
'fast, house, energetic, tense' (all predefined keywords)

now when loading this entry into the update form it should have all predefined keywords with checkboxes by them and the keywords already in will be checked (or a multi selection combobox with the selected values highlighted)- than i can uncheck 'tense' and check 'antheme' and that should update the keywords field to:
'fast, house, energetic, antheme'

I have made an example of what i am looking for using Zoho online database
memimomedia.com/zoho.html
the top bit is a submit form, the bottom is a editable grid
what i would like is something similar to the multi choices box

made some progress - found out about SET data type and changed keywords data type to SET with a list of possible values.
Now DrasticTools seems to support a selction box with DDTYPEKEY and DDTYPEENUM but is there a corresponding DDTYPESET? i need multi selection option here...