Plot graph function in Excel

[dr.slump]

said that I have a function y=f(x) in an interval [x1,x2]. I want to plot the graph in the interval with a step xs.
1 how can I define in Excel a vector [x1:xs:x2], using the step xs?
2 how can then plot the function f?

thanks

[JeteMc]

The easiest way I can think of would be to link the data to a second table on which the graph would be based.
Attached is a simple example.
1. A1:B11 display the original data
2. A20:B30 display the second table where A21:A30 are populated using: =IF(A2<=D$20,A2,NA())
3. B21:B30 are populated using the original function
4. Cell D20 shows the step number to display. (test by changing step number)
Note that the graph used is a scatter chart.
Let us know if you have any questions.