Find next 1 row after row x

Hi all, I've got a matrix of data and need to start at a specific row within the dataset and, based on a condition, select the next 1 row. For example taking this test data:

I need to:

    a = iterate through the dataset and get the value of column 4 that corresponds to column 7 == 0 (i.e. 100)
    starting at position a (100), get the next 1 row of data from column 4 where column 7 == 1 (i.e. 343) and iterate through the data

In this case I would expect 343 to be returned (green).

I hope I've explained it well and any help would be greatly appreciated.

[José-Luis]

This looks like homework. I would start reading up on indexing, particularly logical indexing. Please feel free to ask question here if you get stuck.