How to add data from gnuplot to an existing file without overwiting the contents of said file

I have some gnuplot code as follows:

gnuplot> h=1
gnuplot> a=2
gnuplot> set print "additional numbers.txt"
gnuplot> print h,a
gnuplot> set print

Now I want to add more data to this file without overwritng the previous entry. I can do it in C, but I want to keep everything in 1 script that I can run through gnuplot

I hope you can help.