Thank you Mohamed!
Solution 1, doesn't work because those steps a tou rough. I need 1 cm-steps.
And sorry, I don't understand solutions 2. It creates new fields right? But what is this plugin doing, because creating new fields was possible without that plugin, too. Where is the calculation, that gives me prices for each combination of height and width?
I think i have to add an own price-table for each product. Where can i do that?
Thank you so much!
Edit: The plugin is shown in the joomla-plugins-section now, but not in hikashop-plugins (in system-configuration). Is that correct?