To Preview a Blend Prior to Accepting

From the Features toolbox, select the Blend Feature tool.
With Edge set to Blend, input the proposed radius.
Select the edge to blend.
Accept to view the blend.
The blend is displayed.
If necessary, before accepting the blend, change the values for the radius, or radii, in the tool settings. As each change is input (by pressing <Enter> on the keyboard) the blend preview updates to show the new values.
Accept to place the blend, or Reset to cancel the placing of the blend.
Tip: Even if you make a mistake and accept the wrong blend, you can use the Modify Solid or Feature tool to change the radius.