(ask) firewall rule to block connection-mark="Con Oversea"

RouterOS Beginner Basics
1

hello may I ask for firewall rule to block client connection-mark=“Con Oversea”
as its scrip from http://wiki.mikrotik.com/wiki/How_to_apply_different_limits_for_Local/Overseas_traffic

just copas(copy n paste)
/ ip firewall mangle
add chain=prerouting src-address=192.168.100.0/24 action=mark-connection
new-connection-mark=“Con Entire Traffic” passthrough=yes
comment=“Mark-connection All Traffic” disabled=no
add chain=prerouting src-address=192.168.100.0/24 connection-mark=“Con Entire
Traffic” dst-address-list=!Latvia action=mark-connection
new-connection-mark=“Con Oversea” passthrough=yes comment=“Mark-connection
Oversea Traffic” disabled=no
add chain=prerouting connection-mark=“Con Oversea” action=mark-packet
new-packet-mark=“Oversea traffic” passthrough=no comment=“Mark-packet
Oversea Traffic” disabled=no
add chain=output connection-mark=“Con Oversea” action=mark-packet
new-packet-mark=“Oversea traffic” passthrough=no comment=“Mark-packet
Oversea Traffic” disabled=no
add chain=prerouting action=mark-packet new-packet-mark=“Local Country Traffic”
passthrough=no comment=“Mark-packet Local Country Traffic” disabled=no
add chain=output action=mark-packet new-packet-mark=“Local Country Traffic”
passthrough=no comment=“Mark-packet Local Country Traffic” disabled=no
/ queue simple
add name=“Oversea” target-addresses=192.168.100.254/32 dst-address=0.0.0.0/0
interface=all parent=none packet-marks=“Oversea traffic” direction=both
priority=8 queue=default-small/default-small limit-at=0/0
max-limit=8k/8k total-queue=default-small disabled=no
add name=“Local Country” target-addresses=192.168.100.254/32 dst-address=0.0.0.0/0
interface=all parent=none packet-marks=“Local Country Traffic” direction=both
priority=8 queue=default-small/default-small limit-at=0/0
max-limit=1M/1M total-queue=default-small disabled=no

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  1. how/ what can I ensure(100%) in firewall filter rule to block client for connection-mark=“Con Oversea” ??
    tried for below line but it doesnot work! eg something is wrong
    add chain=forward src-address=192.168.100.254/32 connection-mark=“Con Oversea” action=drop
  2. how to dis/enable ICMP for the connection-mark=“Con Oversea”

PS: I am using internal web-proxy as well, thus its has extra line ie chain=output, is these right?

please advice…

Thank you very much