If your rig is interfaced to TR4W it is possible to use the ctrl-C (and the corresponding ctrl-D) command to send custom messages to the rig.
The following sequences are used (we use the form of the ctrl-C and ctrl-D commands for clarity):

<03>SRS=send_this_string<04>
;sends "send_this_string" to the activeradio

<03>SRSI=send_this_string<04>
;sends "send_this_string" to the inactive radio

<03>SRS1=send_this_string<04>
;sends "send_this_string" radio number 1

<03>SRS2=send_this_string<04>
;sends "send_this_string" radio number 2

For example, most Kenwood rigs use the FL command to control the use of filters, so you might program a key with the sequence

<03>SRS=FL010009;<04>

Pressing this function key during the contest will then cause the rig to switch to the narrow filter.

Other KENWOOD CAT commands

UP. Same function as microphone UP switch

;UP
<03>SRS=UP;<04>

DOWN. Same function as microphone DOWN switch

;DOWN
<03>SRS=DN;<04>

Select filter 8.83 MHz - 500 Гц, filter 445 kHz - 500 Hz

;FILTER 1 = 0.5kHz, FILTER 2 = 0.5kHz
<03>SRS=FL009009;<04>

Select filter 8.83 MHz - 2.4 kHz, filter 445 kHz - 500 Hz

;FILTER 1 = 2.4kHz, FILTER 2 = 0.5kHz
<03>SRS=FL007009;<04>

Select filter 8.83 MHz - 2.4 kHz, filter 445 kHz - 2.4 kHz

;FILTER 1 = 2.4kHz, FILTER 2 = 2.4kHz
<03>SRS=FL007007;<04>

Select VFO A

;VFO A MODE
<03>SRS=FR0;<04>

Select VFO B

;VFO B MODE
<03>SRS=FR1;<04>

Select MEMORY mode

;MEMORY MODE
<03>SRS=FR2;<04>

Turn on FINE STEP

;FINE STEP ON
<03>SRS=FS1;<04>

Turn off FINE STEP

;FINE STEP OFF
<03>SRS=FS0;<04>

Lock transceiver

;LOCK ON
<03>SRS=LK1;<04>

Unlock transceiver

;LOCK OFF
<03>SRS=LK0;<04>

Set memory chanel 2

;SET MEMORY CHANEL 2
<03>SRS=FR2;MC 02;<04>

Set memory chanel 75

;SET MEMORY CHANEL 75
<03>SRS=FR2;MC 75;<04>

Set LSB mode

;SET LSB MODE
<03>SRS=MD1;<04>

Set USB mode

;SET USB MODE
<03>SRS=MD2;<04>

Set CW mode

;SET CW MODE
<03>SRS=MD3;<04>

Set FM mode

;SET FM MODE
<03>SRS=MD4;<04>

Set AM mode

;SET AM MODE
<03>SRS=MD5;<04>

Set FSK mode

;SET FSK MODE
<03>SRS=MD6;<04>

Set CW-R mode

;SET CW-R MODE
<03>SRS=MD7;<04>

Set FSK-R mode

;SET FSK-R MODE
<03>SRS=MD9;<04>

Turn on AIP

;AIP ON
<03>SRS=MX1;<04>

Turn off AIP

;AIP OFF
<03>SRS=MX0;<04>

Set low PITCH

;LOW PITCH
<03>SRS=PT00;<04>

Set high PITCH

;HIGH PITCH
<03>SRS=PT08;<04>

Clear RIT/XIT

;CLEAR RIT/XIT
<03>SRS=RC;<04>

RIT/XIT frequency UP

;RIT/XIT UP
<03>SRS=RU;<04>

RIT/XIT frequency DOWN

;RIT/XIT DOWN
<03>SRS=RD;<04>

Display SWR

;DISPLAY SWR
<03>SRS=RM1;<04>

Display ALC

;DISPLAY ALC
<03>SRS=RM3;<04>

Display dB

;DISPLAY dB
<03>SRS=RM6;<04>

Turn on RIT

;RIT ON
<03>SRS=RT1;<04>

Turn off RIT

;RIT OFF
<03>SRS=RT0;<04>

TX on

;TX ON
<03>SRS=TX;<04>

RX on

;RX ON
<03>SRS=RX;<04>

Generation of synthesized voice

;GENERATION OF SYNTHESIZED VOICE
<03>SRS=VR;<04>

Turn on XIT

;XIT ON
<03>SRS=XT1;<04>

Turn off XIT

;XIT OFF
<03>SRS=XT0;<04>