SAP Web Dispatcher to EXTSVR site

Hi.

I'm having problems getting the SAP Web Dispatcher to redirect to an internal IIS site.  THe Web dispatcher is setup to terminate the SSL connection and redirect to internal SAP servers which is working perfectly but I would like to add the EXTSRV option as seen below and i cant seem to get it to work.

Does anyone have any ideas to try or perhaps what I'm trying is not possible?

~~~~~~~~~~~~~~Profile~~~~~~~~~~~~~~~~~~

SAPSYSTEMNAME = WP1

SAPGLOBALHOST = SAPWebDispatcher

SAPSYSTEM = 00

INSTANCE_NAME = W00

DIR_CT_RUN = $(DIR_EXE_ROOT)\$(OS_UNICODE)\NTAMD64

DIR_EXECUTABLE = $(DIR_CT_RUN)

DIR_PROFILE = $(DIR_INSTALL)\profile

_PF = $(DIR_PROFILE)\WP1_W00_SAPWebDispatche

SETENV_00 = PATH=$(DIR_EXECUTABLE);%PATH%

#-----------------------------------------------------------------------

# Configuration for medium scenario

#-----------------------------------------------------------------------

icm/max_conn = 500

icm/max_sockets = 1024

icm/req_queue_len = 500

icm/min_threads = 10

icm/max_threads = 50

mpi/total_size_MB = 80

#-----------------------------------------------------------------------

# SAP Web Dispatcher Ports

#-----------------------------------------------------------------------

icm/server_port_0 = PROT=HTTP,PORT=0

icm/server_port_1 = PROT=HTTPS,PORT=443

icm/server_port_2 = PROT=HTTPS,PORT=6666

icm/HTTPS/verify_client = 0

icm/HTTP/admin_0 = PREFIX=/sap/admin,DOCROOT=$(DIR_DATA)$(DIR_SEP)icmandir,AUTHFILE=$(icm/authfile),PORT=6234

icm/HTTP/mod_0 = PREFIX=/,FILE=C:\usr\sap\WP1\W00\sec\icm_filter.pfl

#-----------------------------------------------------------------------

# Start webdispatcher

#-----------------------------------------------------------------------

_WD = $(DIR_EXECUTABLE)\sapwebdisp$(FT_EXE)

Start_Program_00 = local $(_WD) pf=$(_PF)

sec/libsapsecu = $(ssl/ssl_lib)

ssf/ssfapi_lib = $(ssl/ssl_lib)

SETENV_01 = SECUDIR=$(DIR_INSTANCE)/sec

is/HTTP/default_root_hdl = abap

wdisp/permission_table = C:\usr\sap\WP1\W00\sec\urlfilter.pfl

wdisp/ssl_encrypt = 0

wdisp/add_client_protocol_header = true

wdisp/system_0 = SID=ZP1, MSHOST=MySAPServer.domain.com, MSPORT=8100

wdisp/system_1 = SID=EXT, EXTSRV=https://MyInternalSite.Domain.com

~~~~~~~~~icm/HTTP/mod_0~~~~~~~~~~~

if %{HTTP_HOST} RegIMatch "MyHostName.com*" [and]
if %{PATH} RegIMatch "^/ZP1*"
SetHeader x-sap-webdisp-target-sid ZP1
RegRewriteUrl ^/ZP1(.*) /sap$1

if %{HTTP_HOST} RegIMatch "MyHostName.com*" [and]
if %{PATH} RegIMatch "^/EXT*"
SetHeader x-sap-webdisp-target-sid EXT

~~~~~~~~~~~~~~~IE ERROR~~~~~~~~~~~~~~~