First of all - thanks for the awesome community. My first post

I am trying to put my watermark on various images, normally the whole process is very simple and easy to execute, automate.
This time, differently, I need to add my watermark on images that are various in dimension. Some are 600*600, some are 900*900 and some 1500*800 etc etc.
I need to resize my watermark according to the size of the image I am applying it to. In other words, watermark needs to keep it's proportion relative to image.
For example, if I am applying watermark on a image with 1000*1000 dimension, watermark needs to be 100*100. If the next image is smaller, lets say 600*600 then watermark needs to shrink down to 60*60 to keep same proportion as previous image.
I did some research and found out it can be done with scripts but I am unable to code it myself and couldn't find any available to use either.
There is an awesome add-in for it Watermark CC but the function I need requires pro version which costs 30 dolars. Since it is a very situational exception, I can't afford to spend that money for one time use.
Any kind of help to set me on the right course is appreciated.