First you need to add a Regular Expression Extractor to extract the value of TOT_GEN_CHG to put it in var TOT_CHG.
Using JSR223 Post processor and Groovy as language:
import java.util.*;
import java.text.*;
DecimalFormatSymbols symbols = new DecimalFormatSymbols();
symbols.setDecimalSeparator(',' as char);
NumberFormat format = new DecimalFormat ("000.00");
format.setDecimalFormatSymbols(symbols);
Float parsed = (Float) format.parse(vars["TOT_GEN_CHG"]).floatValue();
parsed += 100;
vars.put("NEW_VAR", format.format(parsed));
You can then use ${NEW_VAR}
To configure Groovy in jmeter, download it and unzip it, then add embeddable/groovy-all.jar in jmeter/lib folder and restart jmeter.
See example:
<?xml version="1.0" encoding="UTF-8"?>
<jmeterTestPlan version="1.2" properties="2.6" jmeter="2.12-SNAPSHOT.20140413">
<hashTree>
<TestPlan guiclass="TestPlanGui" testclass="TestPlan" testname="Plan testów" enabled="true">
<stringProp name="TestPlan.comments"></stringProp>
<boolProp name="TestPlan.functional_mode">false</boolProp>
<boolProp name="TestPlan.serialize_threadgroups">false</boolProp>
<elementProp name="TestPlan.user_defined_variables" elementType="Arguments" guiclass="ArgumentsPanel" testclass="Arguments" testname="Zmienne zdefiniowane przez użytkownika" enabled="true">
<collectionProp name="Arguments.arguments"/>
</elementProp>
<stringProp name="TestPlan.user_define_classpath"></stringProp>
</TestPlan>
<hashTree>
<ThreadGroup guiclass="ThreadGroupGui" testclass="ThreadGroup" testname="Thread Group" enabled="true">
<stringProp name="ThreadGroup.on_sample_error">continue</stringProp>
<elementProp name="ThreadGroup.main_controller" elementType="LoopController" guiclass="LoopControlPanel" testclass="LoopController" testname="Loop Controller" enabled="true">
<boolProp name="LoopController.continue_forever">false</boolProp>
<stringProp name="LoopController.loops">1</stringProp>
</elementProp>
<stringProp name="ThreadGroup.num_threads">1</stringProp>
<stringProp name="ThreadGroup.ramp_time">1</stringProp>
<longProp name="ThreadGroup.start_time">1399401625000</longProp>
<longProp name="ThreadGroup.end_time">1399401625000</longProp>
<boolProp name="ThreadGroup.scheduler">false</boolProp>
<stringProp name="ThreadGroup.duration"></stringProp>
<stringProp name="ThreadGroup.delay"></stringProp>
</ThreadGroup>
<hashTree>
<Arguments guiclass="ArgumentsPanel" testclass="Arguments" testname="User Defined Variables" enabled="true">
<collectionProp name="Arguments.arguments">
<elementProp name="TOT_GEN_CHG" elementType="Argument">
<stringProp name="Argument.name">TOT_GEN_CHG</stringProp>
<stringProp name="Argument.value">123,23</stringProp>
<stringProp name="Argument.metadata">=</stringProp>
</elementProp>
</collectionProp>
</Arguments>
<hashTree/>
<DebugSampler guiclass="TestBeanGUI" testclass="DebugSampler" testname="Debug Sampler" enabled="true">
<boolProp name="displayJMeterProperties">false</boolProp>
<boolProp name="displayJMeterVariables">true</boolProp>
<boolProp name="displaySystemProperties">false</boolProp>
</DebugSampler>
<hashTree>
<JSR223PostProcessor guiclass="TestBeanGUI" testclass="JSR223PostProcessor" testname="JSR223 PostProcessor" enabled="true">
<stringProp name="cacheKey"></stringProp>
<stringProp name="filename"></stringProp>
<stringProp name="parameters"></stringProp>
<stringProp name="script">import java.util.*;
import java.text.*;
DecimalFormatSymbols symbols = new DecimalFormatSymbols();
symbols.setDecimalSeparator(',' as char);
NumberFormat format = new DecimalFormat ("000.00");
format.setDecimalFormatSymbols(symbols);
//NumberFormat format = NumberFormat.getIntegerInstance(Locale.FRENCH);
Float parsed = (Float) format.parse(vars["TOT_GEN_CHG"]).floatValue();
parsed += 100;
vars.put("NEW_VAR", format.format(parsed));</stringProp>
<stringProp name="scriptLanguage">groovy</stringProp>
</JSR223PostProcessor>
<hashTree/>
</hashTree>
<DebugSampler guiclass="TestBeanGUI" testclass="DebugSampler" testname="Debug Sampler-${NEW_VAR}" enabled="true">
<boolProp name="displayJMeterProperties">false</boolProp>
<boolProp name="displayJMeterVariables">true</boolProp>
<boolProp name="displaySystemProperties">false</boolProp>
</DebugSampler>
<hashTree/>
</hashTree>
</hashTree>
</hashTree>
</jmeterTestPlan>