Hi there.
One possible solution involves the following steps:
1. Select cells A1:A45.
2. Type in the formula =row() and press CTRL + ENTER.
3. Select cells B1:B45.
4. Type in the formula =RAND() and press CTRL + ENTER
5. Select cells A1:B45, press Ctrl C and choose the menu Paste Values Only.
6. With cells A1:B45 selected sort them by column B.
7. Select cells, say, G1:G45.
8. Type in the formula =INDEX(A1:A45,ROW(A1:A45),1) and press CTRL + ENTER.
This will give you fourty-five rows with an integer "randomly" generated
between 1 and 45 without repetition.
Regards,
Otávio