indesign grep : 3 and 4 digit numbers to 5 digits by adding zeros

hello,

in an indesign catalog i would like to change 3 and 4 digit numbers to 5 digits.

3 digit numbers should get 2 zeros up front, 4 digit numbers should get one zero.

5 digit numbers should remain unchanged.

f.i. :

465 -> 00465

5567 -> 05567

23167 -> 23167

i'm pretty sure this can be done by a grep find and replace, but i don't know how.

any help is appreciated.

rené bosch