I don't know whether it is possible but in an ideal world I would like to do the following:

Select a departure point A, B, C, D from a drop down list 1 (so far, so good, I can do that!)

If departure point is A or B only show arrival points 5, 6, 7 and 8 in drop down box 2.

If departure point is C or D only show arrival points 1, 2, 3, 4 in drop down box 2.

Somehow these values should be in my html form but I presume there should be some javascript function called, once the first selection is made in drop down box 1??

I would appreciate any help or advice.

Thanking you in advance.