Hi zan,
I assume that your source data doesn't contain the 2nd column, which indicates the group identification,
e.g., a, b, c,... etc.; but contains only the 1st column to be searches the broken sequence segments.
Could you please try the following formula for the Set Column Values tool for the 2nd column?:((i==1)?1:(col(1)[i]-col(1)[i-1]-1)!=0)?i:col(2)[i-1]
For example, this produces the group identifications which indicate the starting row number of each group; e.g, 1 1
2 1
3 1
4 1
5 1
6 1
7 1
8 1
9 1
10 1
11 1
12 1
13 1
14 1
15 1
21 16
22 16
23 16
24 16
25 16
26 16
27 16
28 16
29 16
30 16
41 26
42 26
43 26
44 26
45 26
47 31
48 31
49 31
50 31
If you need the number of groups and the size of each group, you can simply run the Discrete Frequencies (under "Statistics:
Descriptive Statistics" menu) on the 2nd column.
Hope this helps.
--Hideo Fujii
OriginLab
You was right in your assumption that I had only one col. And the second column where I wrote alphabets was for clarity purpose to explain what I wanted to do. 
Can you bit elaborate on this side too so that I can try making a small worksheet script which would add bit of automation in data analysis. 