Limiting Submission of a Certain Field on a CloudPage

I have a CloudPage being used to collect appointments for a meeting time. I have one CloudPage, and five time slots mapping back to data extension, specifically to the field "Time." "Time" is a text field appearing as a radio button on the form itself.

Can I limit the submissions for each time option? I am familiar with the option to block off the whole CloudPage after it reaches a certain threshold.

I tried the AMPscript below, but I am trying to wrap it around each field instead of the whole form so only that time field is taken off the page upon reaching capacity. I get an error when trying to publish the CloudPage.

%%[SET @rows = LookupRows("AMPSCRIPT", "Time", 2:15pm))set @rowCount = rowcount(@rows)IF @rowCount < 2 THEN]%%<p>sorry maximum has been met</p>%%[ ELSE ]%%--field--%%[ ENDIF ]%%

Is this even possible? Where am I going wrong in the AMPscript?