UI for parameter which can be defined in two different ways

I develop a desktop app with a wizard like dialog which requires several parameters to be set.

Currently all parameters are displayed in a grid with a label and an appropriate control next to it, e.g.

The design problem that I am facing is that there are two parameters (Number of layers and Layer distance) depict the same thing: As the total range is fixed the number of layers is simply the total range divided by the layer distance. When the user changes either value the other one is updated accordingly.

How can I make it clear that those values are interdependent? All the other parameters in the form are not interdependent but have the same appearance.

Should I try to fuse them into a single control? How?

One solution would be to only provide one way to define the value and let the user do the math but this wouldn't be very nice.

Another idea I had was to let the user choose which way to define the value by replacing the label with a combobox which can be set to either Number of layers or Layer distance with the textbox displaying and updating the appropriate value:

but the combobox break up the design as it looks quite different than a label.

Do you have a better idea?