Help with a SED script to replace data in XML file

Good afternoon all,

Please look at the example xml file below.  I am trying to replace and <indicator> if it exists in a certain <frame>.  I know its possible to do this with SED, but I don't have my mind wrapped around the SED control and loop statements well enough to write it.  Below is how I thought it should work written in loose Linux if statements.

TABLENAME="QUOTA_2"
INDICATOR="IND_02"

Read in a line
If (the line equals <frame>),
then
        read in the next line
        If (this next line equals $TABLENAME)
        then
                read in the next line.
                If (this next contains $INDICATOR)***
                then
                        Perform a substitution
                        End the cycle.
                else
                        Read in the next line and,
                        Keep looping back to *** to perform the check.
                        If </frame> is found and match never found. End the cycle.
                fi
        else
        start a new cycle.
        fi
else
        start a new cycle
fi

For example, how can I replace the <indicator id="IND_01"> to be <indicator id="IND_01" mode="off"> in the frame where the name is QUOTA_2.Start Free Trial

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<!--QUOTA_1-->
<frame>
 <name>QUOTA_1</name>
 <entity>
    <name>1</name>
    <alias>2</alias>
    <expr>3</expr>
 </entity>
 <indicator id="IND_01">
    <summary>my summary</summary>
    <description>my address</description>
    <expr>my expression</expr>
    <conf>0.5</conf>
 </indicator>
 <indicator id="IND_02">
    <summary>Fish</summary>
    <description>Pork</description>
    <expr>Beef</expr>
    <conf>3.45</conf>
 </indicator>
</frame>
<!--QUOTA_2-->
<frame>
 <name>QUOTA_2</name>
 <entity>
    <name>1</name>
    <alias>2</alias>
    <expr>3</expr>
 </entity>
 <indicator id="IND_01">
    <summary>my summary</summary>
    <description>my address</description>
    <expr>my expression</expr>
    <conf>0.5</conf>
 </indicator>
 <indicator id="IND_02">
    <summary>Apple</summary>
    <description>Oranges</description>
    <expr>Peaches</expr>
    <conf>10.50</conf>
 </indicator>
 <indicator id="IND_03">
    <summary>Safety</summary>
    <description>Power</description>
    <expr>Freedom</expr>
    <conf>0.50</conf>
 </indicator>
</frame>