plot graph

[junlo]

i need to get data from file "data.txt" and then plot two graph.one graph using the first column and value after 174=XXX, another graph using second column and value 174=XXX. Since my data is very big, so i hv two text box to let user select what data needed to plot in graph.

For example: if value textbox1=3.8566300, textbox2=100.81888000
i need to get data from (3.8566300 -0.0001) to (3.8566300+0.0001)
From (100.81888-0.0001) to (100.81888+0.0001)
and then plot the graph.

Format in "data.txt"
3.85663000 100.81888000 174=0
3.85625000 100.81778000 174=0
3.85519000 100.80883000 174=0
3.85425000 100.80501000 174=0
3.85252000 100.80040000 174=0
3.84993000 100.79627000 174=0
3.84648000 100.79283000 174=0
3.83853000 100.78786000 174=0
3.83705000 100.78591000 174=0
3.83669000 100.78409000 174=0
3.83646000 100.77324000 174=0