livecode - Replacement only between begin{document} and \end{document} -

i have got of code stack-overflow , it's working, while changing code requirement(replacement between begin{document} , \end{document}) it's not working

this code got

put wordoffset("begin{document}",fld "mytextfield") tbegin put wordoffset("end{document}",fld "mytextfield") tend put replacetext(word tbegin tend of fld "mytextfield","bad","good") word tbegin tend of fld "mytextfield" 

i using following code. how convert above code requirement.

  on mouseup         put htmltext of field "mytextfield" myhtml         set casesensitive true         put field srtext myarraytobe         split myarraytobe cr         put number of lines of (the keys of myarraytobe) myarraylength        repeat = 1 myarraylength            put  myarraytobe[i] y           split y colon           put y[1] searchstr           put y[2] replacestr           if searchstr empty              put  0 m           else            replace searchstr  "<strike><font bgcolor=" & quote & "yellow" & quote & ">" & searchstr & "</font></strike><font bgcolor=" & quote & "green" & quote & ">" & replacestr & "</font>" in myhtml         end if      end repeat       set htmltext of fld "mytextfield" myhtml        end mouseup 

now think understand problem, try this...

on mouseup     put htmltext of field "mytextfield" myhtml     ## first need break myhtml 3 parts can edit "document" part...    -- find document "begin" marker , put it's position tbegin variable    put wordoffset("begin{document}",myhtml) tbegin     -- find document "end" marker , put it's position tend variable    put wordoffset("end{document}",myhtml) tend      put word 1 tbegin of myhtml theader -- part 1    put word (tbegin +1) (tend -1) of myhtml tdocument -- part 2 = document change    put word tend -1 of myhtml tfooter -- part 3     set casesensitive true     put field "srtext" myarraytobe     split myarraytobe cr     put number of lines of (the keys of myarraytobe) myarraylength    repeat = 1 myarraylength        put  myarraytobe[i] y       split y colon       put y[1] searchstr       put y[2] replacestr       if searchstr empty          put  0 m       else           replace searchstr  "<strike><font bgcolor=" & quote & "yellow" & quote & ">" & searchstr & "</font></strike><font bgcolor=" & quote & "green" & quote & ">" & replacestr & "</font>" in tdocument       end if    end repeat      ## can rebuild htmltext 3 parts , put in field...    set htmltext of fld "mytextfield" theader && tdocument && tfooter end mouseup