Switching from 2/4 to 7/8 then 6/8

Hallo and pardon my english...

I have to create a score which starts in 2/4, goes to 7/8, then 6/8. The problem arises with 7/8: it seems that I can create a score in this metre, but I cannot find a way to insert this kind of tempo in a score which begun otherwise. I tried to write the 2/4 part in a different file and paste it at the beginning, but it did not work, I found that part "translated" in 7/8. The same problem applies writing the 7/8 period and pasting it in the 2/4 score...

Any suggestion?

Thanks!