How to switch the input data from workspace into Simulink as the time goes on?

In general, Simulink is able to work well with the predefined input data, using the 'From Workspace' block. However, in my system, the data input to the simulink model should vary with time. To be more specific, at this moment, the model gets this series of data as input and at next moment, the model should get another series of data as input. These two series of data are stored in two variables and some conditions are met to switch the input data. Any smart ideas would be appreciated:)