I use predefined settings for fillets that I have to do most often.
(defun C:F1 () (frx "0.0625"))
(defun C:F2 () (frx "0.125"))
(defun C:F3 () (frx "0.250"))
(defun C:F4 () (frx "0.375"))
(defun C:F5 () (frx "0.500"))
(defun frx (x / *error* ofr)
(defun *error* (errmsg)
(if (not (wcmatch errmsg "Function cancelled,quit / exit abort,console break"))
(princ (strcat "\nError: " errmsg))
) ; if
(setvar 'filletrad ofr)
)
(setvar "cmdecho" 0)
(setq ofr (getvar 'filletrad))
(vl-cmdf "_.Fillet" "R" x "_.Fillet" "_multiple")
(setvar "cmdecho" 1)
(princ (strcat "\nFillet (radius=" x "): Select first entity or [fillet Settings.../Polyline/Radius/Trim/Undo/Multiple]:"))
(while (> (getvar 'cmdactive) 0) (command pause))
(setvar 'filletrad ofr)
(princ)
)