The insulinConcentration is a parameter in the original model, so that can't vary over time. However, it can easily be changed to an input that you can control.
In the attached model, I have set the insulin.c variable to filter.y, which takes its input from the new insulinConcentration Real input.
The filter is needed to avoid SystemModeler trying to take the derivative of an input.
With the attached model, you can do:
Attachments:
