I'm not sure what text it is you want to change. If you want to change the name of a berry item, you can simply use Item Manager or the
Gen 3 Tools' Item Editor to change the names. If you want to change the name of the berry-holding part of the bag, however, then this is what you should do (or if you want to edit any text, really):
Download
a .tbl file,
Translhextion,
XSE 1.1.1 and
HxD (because Translhextion's interface and general usability is awful).
Load your ROM in Translhextion, and then .tbl file in Translhextion (Ctrl + T). Check "Thingy View Active". Do the shortcut Alt + F and enter the text for the bag's name, exactly: "BERRIES". Cycle through until you find one that is surrounded by the other names used in the bag, such as KEY ITEMS. Take note of the offset of the letter "B" in Notepad or something (it's 0x410762 in a vanilla Ruby ROM).
Close everything and then load your ROM in XSE. Create a script like this:
Code:
#dynamic 0x800000
#org @string1
= Berry Pouch
Of course, enter whichever string you wish.
Compile it and take note of the offset. Close XSE.
Take the first offset (0x410762) and convert it to a pointer, like so:
410762
[41][07][62]
[62][07][41]
[62][07][40] + [08]
62074008
Do this to the second, new offset as well.
Load your ROM in HxD. Do the shortcut Ctrl + R. In the first field, enter 62074008, and in the second, the pointer to your new string (if it was compiled at 0x800000, the pointer would be 00 00 80 08). Change "Text string" to "Hex values" and click "Replace all". Save your ROM.