Hi!
I work on the Control Design Group in LabVIEW and, first of all, thank you for your interest in using the Control Design Toolkit.
If I understand the problem that you are trying to solve, you have a set of data (gain vs frequency) and you want to know the frequency response of you system. Well, the gain vs frequency is the frequency response of it. To obtain a graph of this, you can use a XY graph in LabVIEW and plot the frequency against the gain to obtain the bode plot. In general you need to change the X-Scale to Log and modify gain to be in dB (multiply the gain by 20*log(G)), but this should be enough to give you the bode response.
The CD Bode.vi, as most of the other functions available in Control Design Toolkit, needs to have a model in State-Space, transfer function or zero-poles-gain format. So, if you already have a model in Laplace or z-transform, you can easily use the Control Design Toolkit to obtain the bode plot. However, for what you are trying to do, it will not help you to plot the frequency response.
Now, if you are interested to know the transfer function coefficients of a specific system, the right toolkit is the System Identification Toolkit. It would allow you to obtain the coefficients from input/output signals of a system. To obtain better results for this toolkit, a square wave or noise signal should be applied to the system and measured at the same time. The function ARX, for example, gives you the coefficients based on this signals. I think this is the right toolkit to obtain the linear model of a system that you only can do experiment with it.
I hope this can help you to understand the different uses of our tools. Please let me know if you have any more question and I will be happy to help you!
Barp - Control, Simulation, RTT and HIL - National Instruments