How would i get this intended output in a cell?

[jcbv3]

8:00	60
8:30	79
9:00	79
9:30	100
10:00	100
10:30	50
11:00	50
11:30	50
12:00	100
12:30	100
13:00	100
13:30	50
14:00	50
14:30	50
15:00	100
15:30	100

<colgroup><col width="64" span="2" style="width:48pt"> </colgroup><tbody>
</tbody>

I have these data in 2 columns. I was wondering what formula I could use to have the below as the output:

0800-0930, 1030-1200, 1330-1500

==========

Basically, I would like to group the ones that are below 100.

 

[bobsan42]

Let's assume you have the hours in col A, starting from A2 down
The numbers in col B starting down from B2.
To make the formula work and keep it as simple as possible put the number 100 in cell B1.
The data order must not change.

in cell C2 place the following formula:

=IF(B2<100,IF(B1>=100,C1&IF(ISBLANK(C1),"",",")&TEXT(A2,"hhmm-"),C1),IF(B1<100,C1&TEXT(A2,"hhmm"),C1))

Now fill it down to the end of the data.