Editing/adding actionscript as bytecode

I have a problem with an actionscript as bytecode of a modified version of the swf file. I want to add a moving shadowlayer with the help of a tileable texture. So my idea to create to frames, the first one include the old frame, the second one moves the x-coordinate and after that jumps back the first frame (with the new coodinates). But cause the swf file was edited (very similar, but i cant use regular decompiler), I have to write the bytecode. Does anybody have an idea how to realize this moving shadow layer?

Heres the part of the code (the actionscript include only the gotoframe part):

<sprite id="10">

     <frames>

          <frame id="0">

               <placeobject depth="1" character="7" rotm00="1.000000" rotm01="0.000000" rotm10="0.000000" rotm11="1.000000" tx="0.000000" ty="0.000000" red="255" green="255" blue="255" alpha="255" ratio="0.000000" clipdepth="-1" unknown="0">

                    <poflags value="HasCharacter|HasMatrix|HasName"/>

                    <poname name="Shadow1"/>

               </placeobject>

          </frame>

          <frame id="1">

               <placeobject depth="1" character="-1" rotm00="1.000000" rotm01="0.000000" rotm10="0.000000" rotm11="1.000000" tx="0.000000" ty="0.000000" red="255" green="255" blue="255" alpha="255" ratio="0.000000" clipdepth="-1" unknown="0">

                    <poflags value="HasMatrix|Move"/>

               </placeobject>

          </frame>

          <frame id="3">

               <action>

               <gotoframe frame="1"/>

               <end/>

               </action>

          </frame>

     </frames>

</sprite>