maven compiler plugin + toolchains

[intel radoux]

Hello,

I wish to set something like this in my parent pom :

           <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-toolchains-plugin</artifactId>
                <version>1.1</version>
                <configuration>
                    <toolchains>
                        <jdk>

<version>${project.build.pluginsAsMap(org.apache.maven.plugins:maven-compiler-plugin).configuration.children[0].value}</version>

                        </jdk>
                    </toolchains>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>toolchain</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

so that I can only set the source level in one place. The idea is that I
can set another level in one child module and toolchain will select the
correct JDK.
             <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                </configuration>
            </plugin>

unfortunatly this don't work has ${project.build....... } is not resolved
when set in configuration element.
Do somebody have another idea on how to set this ? (why toolchain doesn't
work hand on hand with compiler plugins ? )

Thank you