Replace text in applescript with applescript.

Question

I'm trying to start a script that changes part of another script as it needs to alter slightly each day,
I need to replace this line of the script that I am holding in the resources (so never changes)
choose from list ItemTypesList with prompt "Choose Item" default items {"ER"}
I need to change the part that is ER to the ItemType
choose from list ItemTypesList with prompt "Choose Item" default items {"ItemType"}
Then save in a different location with overwriting?
I managed to get so far but having difficulty get it to find and replace and then save.
the find and replace is borrowed from another script I found (but for text editor)
Many Thanks
Matt
set theScript to (path to me)'s POSIX path & "Contents/Resources/EverythingCropProcess.scpt"
set saveScript to (path to home folder)'s POSIX path & "Workflow/EverythingCropProcess.scpt"
log theScript
set ItemTypesList to {"ER", "ER multi stud", "NeckWear", "Ring", "WristWear"}
choose from list ItemTypesList with prompt "What are you mostly working on today?"
if the result is false then
          return
else
          set ItemType to result as text
  log ItemType
end if
replaceText("choose from list ItemTypesList with prompt \"Choose Item\" default items {\"ER\"}", "choose from list ItemTypesList with prompt \"Choose Item\" default items {\"" & ItemType & "\"}", theScript)
on replaceText(search_string, replacement_text, this_document)
          tell application "AppleScript Editor"
  open this_document
                    set AppleScript's text item delimiters to the search_string
                    set this_text to the text of the front document as list
                    set AppleScript's text item delimiters to the replacement_text
                    set the text of the front document to (this_text as string)
  save saveScript
          end tell
end replaceText

Answer 1

I think I might be getting a little confused
This is the scipt to run at login (as an app)
set scriptToModify to load script ((path to me)'s POSIX path & "Contents/Resources/Scripts/defaultScript.scpt")
set scriptToModify's ItemTypesList to {"ER", "ER multi stud", "NeckWear", "Ring", "WristWear"}
choose from list ItemTypesList with prompt "What are you mostly working on today?"
store script scriptToModify in ((path to home folder)'s POSIX path & "Workflow") with replacing
Then this is the script held in the bundle
set ItemTypesList to {"ER", "ER multi stud", "NeckWear", "Ring", "WristWear"}
choose from list ItemTypesList with prompt "Choose Item" default items {"XXXXX"}
--the XXXXX part above is the area i hope to change.
if the result is false then
          return
else
          set ItemType to result as text
          if ItemType is equal to "ER" then
                    set BorderIncrease to 40
          else if ItemType is equal to "ER multi stud" then
                    set BorderIncrease to 20
          else if ItemType is equal to "NeckWear" then
                    set BorderIncrease to 10
          else if ItemType is equal to "Ring" then
                    set BorderIncrease to 40
          else if ItemType is equal to "WristWear" then
                    set BorderIncrease to 20
          end if
end if