change excel columns to letters

6:38

5:36

4:22

4:53

5:03

5:45

6:15

5:36

1:45

2:01

4:49

2:42

4:36

9:07

5:37

4:39

8:33

7:03

4:53

7:54

3:18

5:48

4:12

2:59

14:05

16:49

2:47

2:47

1:12

5:26

10:01

4:20

5:20

47:29

29:46

5:07

4:20

1:15:09

10:00

47:29