curve inflection point

Hi everybody!

I am in search of a possibility to control the inflection point of curves which means for example i want to intersect two curves at their inflection points. Unfortunately i do not exactly know how to handle this problem because if i change the shape of the curve for ex. by searching the closest inflection point and moving these points half way...the inflection point changes immediately. Do i have to find a solution via. galapagos or hoopsnake...i also thought about the kangaroo powerlaw component but it doesn't work with curves? Are there any mathematical solutions for this...for ex. by keeping the tangent of the inflection point. Thanks in advance for your hints!

David