gnuplot: insert custom xtic label amidst otherwise regular tic intervals

I'm actually using orgmode to export, so my data is simply in org-table form; that shouldn't matter. It's like so: ``` | Time | Video | Presentation | Paper | |-------+-------+--------------+-------| | 0 | 0 | 0 | 0 | | 20 | 54 | 63 | 38 | | 31.25 | 72 | 81 | 44 | | 33. | 83 | 89 | 49 | | 34. | 95 | 101 | 54 | | 36.5 | 102 | 112 | 59 | ``` This is for work, and I'm plotting file downloads over the number of hours since they were made available. An effort was made to point people toward these files at t=28hrs, and I wanted to have a custom tick there matching a vertical line so I could call attention to that and show the downloads before and after the publicity effort. Thus, my gnuplot code looks like so: ``` set title "File Downloads" set xlabel "Time Since Posting (hrs)" set xrange [0:40] set xtics 0,5,40 set ylabel "Downloads" set yrange [0:125] set ytics 0,25,125 plot data u 2:3 w l lw 2 lc 1 title 'Video', \ data u 2:4 w l lw 2 lc 2 title 'Presentation', \ data u 2:5 w l lw 2 lc 3 title 'Paper ``` I'm aware that one can do something like ``` set xtics ("0" 0, "10" 10, "Event" 30, "40" 40) ``` But I don't really want to do that for all my tics, especially since this will be an ongoing plot and I don't know how far in time I'll track things. Can I specify a regular set of intervals like the above, but then call out a custom tic on top of the axis somehow amidst those pre-defineid tics? This won't work, but for example: ``` set xtics 0,5,40; ("Event" 30) ``` Thanks for any suggestions.