I would like to implement a transfer function into a model based component

I tried to use differential equation in a model using only mathematical relationship (without using the graphical representation and the function connect()) but with no success. In this post, I got blocked by the compiler as my system was over-determined since I added the differential equations.
So instead of using differential equation, my new idea is to use transfer function, so:
- There will be a relationship between my input and output current (i2 = H * i1)
- There will be a relationship between my input and output voltage (v2 = H * v1)
But I have no idea how to proceed.
Thanks in advance for your help, and if you have any other suggestion or idea, feel free to share
Best regards