Ah. You have made a custom object which CALLS an object from the AC25 library.
A quick but temporary solution that might work would be to add the AC25 Migration Library to your file. Not quite sure if this will actaully work as the names of objects in the migration library do not actually match the original...
Better, would be to update your custom object itself but changing the call to "Window 26". Updating it to work with AC26 in this way will prevent it from working with previous versions if it is still being used there.
CALL "Window 25"
CALL "Window 26"
If you need it to work in multiple versions, open the object in your oldest AC, and create a new Text Parameter with the value "Window 26", if that will be your primary AC version and replace the call with your parameter name. Once done, when you open the object in alternate AC versions, you can just edit the parameter to match the current AC version. So if you open it in AC25, you would type "Window 25" into that parameter.
CALL "Window 25"
CALL newtextparameter
If you are really confident, you could possibly automate this by querying the AC version then constructing a string from that to insert into the CALL.
Ling.
