Hi Harish,
when you use inports, you will typically set something like [t, u] as inputs, so I suppose what you want to do is define t and u or whatever you call these variables from a spreadsheet? In that case, I would perform steps like importing the spreadsheet and extracting t and u from this in a model callback, see https://www.mathworks.com/help/simulink/ug/model-callbacks.html.
Best wishes,
Harald
