Hello.  I'm trying to summarize some numeric data based on its location
relative to a label field.  I have a set of surveys.  For each survey there
are three relevant columns of data (LABEL, DISTANCE, and DEPTH).  Not all the
values have labels, and each survey has a different number of entries.  
 What I'd like to do is be able to sum the depths BETWEEN two labels so a
script  would have to look for the start label (LBF) - then go to the next
cell (LBF + 1) and begin summing depth values until the value one cell before
the stop label (RBF - 1).  For any given survey this can be done easily with
an expression.  But I have been unable to get the start-stop pieces to work.  
A sample is below. thanks - e

LABEL    DIST_LB    DEPTH
LBPIN    0       99.32
        0.5         99.24
LBF    0.95       99.08
BLB    0.95       98.63 --- Start summing here
LEW    1.15       98.62
       1.55    98.57
       1.95    98.57
       2.35    98.61
       2.75    98.58
       3.15    98.55
       3.55    98.55
       3.95    98.45
T       4.35    98.41
       4.75    98.42
BRB/REW    5.15    98.61
RBF        5.4    98.88 --- Stop summing here
        5.9    98.91
        6.4    98.95
        6.9    99.02
        7.4    99.13
RBPIN    7.91    99.1