Financial dimension lookup in form level in Ax 2012

public void lookup()
{

    DimensionAttribute                            dimensionAttribute;
    DimensionAttributeDirCategory       dimAttributeDirCategory;
    Query                                                 query = new Query();
    QueryBuildDataSource                      qbds;
    SysTableLookup                               sysTableLookup;

    dimensionAttribute     = DimensionAttribute::findByName('Products');
    if (dimensionAttribute.Type == DimensionAttributeType::CustomList)
    {
        select firstonly DirCategory from dimAttributeDirCategory
            where dimAttributeDirCategory.DimensionAttribute == dimensionAttribute.RecId;

        sysTableLookup = SysTableLookup::newParameters(tableNum(DimensionFinancialTag), this);
        sysTableLookup.addLookupfield(fieldNum(DimensionFinancialTag, Value));
        sysTableLookup.addLookupfield(fieldNum(DimensionFinancialTag, Description));

        qbds = query.addDataSource(tableNum(DimensionFinancialTag));
        qbds.addRange(fieldNum(DimensionFinancialTag, FinancialTagCategory)).value(queryValue(dimAttributeDirCategory.DirCategory));

        sysTableLookup.parmQuery(query);
        sysTableLookup.performFormLookup();
    }

}
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1.)create New Class...................
class  NaSyslookup extends SysLookup
{
}
Public void lookupDimension(FormStringControl _stringControl, Name _dimensionName)
{
     syslookup::lookupDimension(_stringControl,_dimensionName);
}

2.)write code in Lookup override...........................

public void lookup()
{
    NaSyslookup cicsyslookup        = new NaSyslookup();
    Query query = new Query();
    QueryBuildDataSource queryBuildDataSource;
    SysTableLookup sysTableLookup =  new SysTableLookup();
    //super();
    switch (TransType.selection())
    {
        case 0:
            sysTableLookup =                  SysTableLookup::newParameters(tableNum(DimAttributeOMBusinessUnit), this);
            queryBuildDataSource = query.addDataSource(tableNum(DimAttributeOMBusinessUnit));
            sysTableLookup.addLookupfield(fieldNum(DimAttributeOMBusinessUnit, Value),true);
            sysTableLookup.addLookupfield(fieldNum(DimAttributeOMBusinessUnit, Name));
            sysTableLookup.addSelectionField(fieldNum(DimAttributeOMBusinessUnit, Value));
            sysTableLookup.parmQuery(query);
            sysTableLookup.performFormLookup();
            break;

        case 1:
            sysTableLookup = SysTableLookup::newParameters(tableNum(DimAttributeOMDepartment), this);
            queryBuildDataSource = query.addDataSource(tableNum(DimAttributeOMDepartment));
            sysTableLookup.addLookupfield(fieldNum(DimAttributeOMDepartment, Value),true);
            sysTableLookup.addLookupfield(fieldNum(DimAttributeOMDepartment, Name));
            sysTableLookup.addSelectionField(fieldNum(DimAttributeOMDepartment, Value));
            sysTableLookup.parmQuery(query);
            sysTableLookup.performFormLookup();
            break;

        case 2:
            sysTableLookup = SysTableLookup::newParameters(tableNum(DimensionFinancialTag), this);
            queryBuildDataSource = query.addDataSource(tableNum(DimensionFinancialTag));
            sysTableLookup.addLookupfield(fieldNum(DimensionFinancialTag, Value),true);
            sysTableLookup.addLookupfield(fieldNum(DimensionFinancialTag, Description));
            sysTableLookup.addSelectionField(fieldNum(DimensionFinancialTag, Value));
            sysTableLookup.parmQuery(query);
            sysTableLookup.performFormLookup();
            break;

 default:
    }
}