APEX

Having spent the entire morning on the interweb googling I'm still at a loss as to how to acheive this

I am on apex version 4.01

I suspect if I was on 4.2 I could do this by dynamic actions , oh well

possibly I could use javascript to loop through each row check the value of the field and then make each item disabled/readonly

cannot seem to find an example that I can understand enough to tweak

basically I have developed a tabular form that the client loves with nice formatting , calculated values in the column headings that I'm quite proud of :-)
row highlighting depending on values etc but one final request eludes me

we have three rows that we need to lock so that the user cannot amend the values in the text fields
in the column PM_REF we have a value , if the value is 200,300 or 400 then all the items in the row should be disabled or readonly

hopefully someone can put me out of my misery so I can complete this form ,

many thanks

Chris