JMP table cell references are pretty easy. If you have read in a table with this command:
dt = open database(dsn_string, "select * from mytable");
Suppose you want the value of the last row for the column called Timestamp. You can reference that cell with syntax like this:
lr = nrows(dt);
one_cell = dt:timestamp[lr];
one_cell = column(dt, "Timestamp")[lr];
current data table(dt); // need this to insure we're looking at the right table
one_cell = :Timestamp[lr];
one_cell = :name("Timestamp")[lr];