How to sum groups of contiguous values automatically?

[jaleahmad]

Note: The number of values in the group can be anything between 1 and 1000. The list of values is preceded by the keyword "start"
Is there a formula to calculate the total?
Example of data:

start
1
2
1
1
2
3
1
2
Total=?

<tbody>
</tbody>

 

[jaleahmad]

correction: (actually the data has more than one group)

start
1
2
1
1
2
3
1
2
Total=?
start
1
2
11
1
2
Total=?
start
1
2
1
Total=?

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