Use the "onchange" event of that editbox to call a method in your script. Have another editbox for radius_ft on your form.Sub DisplayFeet()
Dim objControl, objPage, Meters, Feet
'Get the control, page objects
Set objControl = ThisEvent.Object
Set objPage = ThisEvent.Object.Parent
Meters = objControl.Value
Feet = Meters * 3.2808399
'Display the value on a editbox control named "edtFeet" on the same page
objPage.Controls("edtFeet").Value = Feet & "ft"
End Sub
Not tested but should get you where you want to go.