I am attempting to write a batch file (to be executed at startup) to enable
or disable a given user account based on the current time. My efforts thus
far have resulted in this:

if %time% geq 15:30 if %time% lss 10:00 net user username  /active:yes
if %time% geq 10:00 if %time% lss 11:55 net user username /active:no
if %time% geq 11:55 if %time lss 12:35 net user username /active:yes
if %time% geq 12:35 if %time% lss 15:30 net user username /active:no

If the time is from 3:30 PM to before 10:00 AM, or from 11:55 AM to before
12:35 PM,  the account should be enabled. If the time is from 9:55 AM to
before 11:55 AM, or from 12:35 PM to before 3:30 PM, the account should be
disabled. In conjunction with a few sheduled tasks, this batch file would
enable the given account to be unavailable to users except at the desired
times, without the restrictions of the '/times' option for the 'net users'
command.
The only problem, naturally, is that the batch file doesn't work. The second
line returns 'net was unexpected at this time', and the last line doesn't
seem to run at all. What am I doing incorrectly?