Find smooth position for edge loop

Hi,

I need to find a smooth position for an edge loop that is between two other edge loops, however using “w+smooth” does not
scale or smooth the loop to the proportion I am looking for. (difficult question to ask without the actual example). Basically
I keep having to move vertices manually and am looking for easier ways.

What is the proportion that you are looking for? A screenshot would be nice.

select the edge loop with the alt key. press G G to start sliding it. now look in the header at the instructions. E will match one side, E then F will match the other side, as you slide. Probably you know this already and are asking something else?