You should look at the initget and getkword functions.
Code:
(DEFUN C:JHKINSERT ( / attdia jp1) localize those variables!
(setq attdia (getvar "attdia"))
(setvar 'attdia 0)
(initget "FD1 FD2")
(setq jp1 (strcase(getkword " [FD1/FD2]: ")))
(COND
((= "FD1" JP1)(princ "\nFD1 = "))
((= "FD2" JP1)(princ "\nFD2 = "))
((= "FD1" JP1)(command "-insert" "c:\\JHK_MEP\\BLOCKS\\FD1.DWG" PAUSE "" "" "" "" ))
((= "FD2" JP1)(command "-insert" "c:\\JHK_MEP\\BLOCKS\\FD2.DWG" PAUSE "" "" "" "" ))
(T(princ "\nInvalid input"))
)
(setvar 'attdia attdia)
(princ)
)
Then you can either pick your option with the mouse or type it in.