Specifying Environment Variables at Deploy Time not at Build Time

Deploy Time Command Line 1

MyProject.deploy.cmd
/y /M:https://MyHostMachine:8172/MsDeploy.axd
/u:MyUserName /p:MyPassword /A:Basic -allowUntrusted 
"-setParam:name='IIS Web Application Name',value='MyIISWebAppName'"

Generated by Build MyProject.SetParamters.xml 1

<?xml version="1.0" encoding="utf-8"?>
<parameters>
  <setParameter name="IIS Web Application Name" value="Default Web Site/MyWebProject_deploy" />
  <setParameter name="MyDatabase-Web.config Connection String" value="MyDefaultConnectionString" />
</parameters>

Generated by Build MyProject.SetParamters.xml 2

<?xml version="1.0" encoding="utf-8"?>
<parameters>
  <setParameter name="IIS Web Application Name" value="Default Web Site/MyWebProject_deploy" />
  <setParameter name="MyDatabase-Web.config Connection String" value="MyDefaultConnectionString" />
  <setParameter name="My Service Url" value="http://MyTestServiceUrl.com/" />
</parameters>

Parameterised Deploy Time Command Line 2

MyProject.deploy.cmd
/y /M:https://%Target.MachineName%:8172/MsDeploy.axd
/u:%Target.Username% /p:%Target.Password% /A:Basic -allowUntrusted 
"-setParam:name='IIS Web Application Name',value='%Target.IISApplicationName%'"
"-setParam:name='My Service Url',value='%MyServiceUrl%'"

parameters.xml

<?xml version="1.0" encoding="utf-8"?>
<parameters>
  <parameter name="My Service Url" description="" defaultValue="http://MyTestServiceUrl.com/">
    <parameterEntry kind="XmlFile" scope="Web.config" match="/configuration/appSettings/add[@key='MyServiceUrl']/@value" />
  </parameter>
</parameters>