B² Spice v.5 Live Circuit Parameters 

see a movie of B2 Spice's Live Parameters in action

Oddly named, but quite useful, pressing the Parameter tab reveals a small spreadsheet-like grid which lists all the parts in the circuit available for scrutiny (actually, only those parts which allow value changes, such as resistors, capacitors, current and voltage sources, and inductors, but not ground). Thus, the part’s name is displayed in the left cell, while its value is displayed in the right cell.

Clicking on the value allows the user to edit the value by typing in a new value or using the slider at the top of the tab to control the value. By using this in conjunction with a running Simulation, you can see what effects changing a parts values will have to the function of the circuit immediately using either the Circuit Visualizations or Virtual Instruments.