How to train neural network with feedback with transform function

Hello,

I have to build a ANN model with 5 inputs (input1, input2, input3, input4, input5,) and 1 target (target1).

where the input5i = target1i-1 * const

here const is from lookup table using input1i-1.

I tried using NARXnet but not able to introduce the transfer function before feeding back the input5i (calcualted using traget value of previous time in series).

Question: Is it possible to have transfer function while feeding back one of the input?