How to train a neural network model in python or any language that can train itself from a excel file and validate itself also from a excel file?
You are mentioning two different problems:


data gathering: here you want to get your data from an excel file for both the training and the validation
modeling your data: here you want to do it with a neural network.


For the data gathering, I suggest you to use pandas, a python library which can extract data from excel files with pandas.read_excel as well as many other source (csv files, parquet files). Then once you have the data in python you can  try to understand them with a neural network. The book I used to learn it was handson machine learning by Aurelien Gueron (https://github.com/ageron/handson-ml). Hope you will find this useful. 

Before going to neural network you should also have a look at scikit learn a python library which is used for machine learning when you do not have enough data to train a neural network, if you are getting you data from excel files I guess you have less than 100 thousand data rows which might be a bit too few to train a neural net.