Hi,
You can follow the steps below to visualize Excel sheet data in Scope block in Simulink:
1) Load the excel sheet in form of a table in MATLAB workspace. You can refer to the following MathWorks documentation to understand more about how to load Excel sheet data in the workspace:
2) Since you want to plot two variables let us say a and b, you can create a time vector which can be used as a common time reference for both the variables.
3) You can use Simulink's From Workspace block to input data from workspace into Simulink. Connect the output of the From Workspace blocks to the input of the Scope block as shown below:
4) Simulate the model and view the output of the Scope block. For the data that I have used, the output is shown below:
I hope this helps.