default values for select options

This question was asked in interview

I have define a select options say

select-options svbeln for vbak-vbeln.

I want to set 2 default values ranges for above select options

1st range of default value should be say, svbeln-low is 1 and svbeln-high is 20 it should be exclusive of 16.

the second range of default value should be svbeln-low 50 and svbeln-high is 60 exclusive of 55

when the user execute the report and press f4, it should display this 2 ranges by default

correct solutions will be rewarded appropriately.

thanks

Sanjay