Change the input of a standard block

Hello to everybody,

in some standard blocks it is possible to change some signals from internal to external.

For example if you use the standard block 'Sine Wave' from the Simulink sources library, you can choose for the Time (t) on the one hand the 'simulation time' or on the other an 'external signal'.

In my case I am using the 'Fourier' block from the Simpowersystems library. See link below:

Fourier

In dependence of the input of the different values, e.g. 'Fundamental frequency' or 'Harmonic', the layout of the subsystem changes. In my case I want to vary the frequency of my signal from time to time. Is it possible to change the standard block to use the 'Fundamental frequency' from an external signal? Because the 'Fundamental frequency'is used in the different subsystems with the variable: '2*pi*Freq*sps.n' or 'sps.Freq'. In general it is hard to understand the syntax of using inherited signals in a subsystem. I could add an additional input to the block, but then I have to add the signal also to the different subsystems. In case it is possible to change an internal value to an external source it would be much easier.

I know that during the change of the frequency the output has an error, but only for one period because the change of frequency is very fast.

I hope I explained my problem good enough to get some help!

Thanks in advance!

Max