Instead of delete and re-add, you could replace the string.
How:
[edit]
user# edit system services dhcp pool 192.168.100.0/24
[edit system services dhcp pool 192.168.100.0/24]
user# replace pattern 192.168.100.254 with 192.168.100.200
Regards,
Raveen
Note: If this answers your question you could mark this post as accepted solution, that way, it benefits others as well. Kudos will be cool if I deserve it!