Dichiarare una variabile con nome di campo all'interno di una stored p.

[net-level]

[Database MySQL]
Salve
Ho una stored procedure che deve eseguire una query, all'interno della quale devo filtrare per un campo diverso a seconda del parametro passato, il problema è che se passo la stringa con gli apici non viene riconosciuta nella query, mentre se la passo senza apici mi genera un errore, vi indico un esempio:

BEGIN
DECLARE vrData VARCHAR(20) DEFAULT 'tbcontr01.CRSRATA';
if decor=1 then
set vrData = 'tbcontr01.CRSCAD';
elseif decor=2 then
set vrData = 'tbcontr01.CRDECOR';
 end if;


SELECT tbcontr01.CRID, tbcontr01.CRTIMEST, tbcontr01.CRNUM, tbcontr01.CRKRIID, tbcontr01.CRKSTID, tbcontr01.CRDECOR, tbcontr01.CRKFZID, tbcontr01.CRSCAD, tbcontr01.CRSRATA, tbcontr01.CRDFIRMA, tbcontr01.CRDSTAT, tbcontr01.CRNTAC, tbcontr01.CRPOLIE, tbcontr01.CRRATEO, tbcontr01.CRPROVVF, tbcontr01.CRPROVV, tbcontr01.CRCARAT, tbcontr01.CRSPEC, tbcontr01.CRMORA, tbcontr01.CRDANN, tbcontr01.CRDSOSP, tbcontr01.CRKCANID, tbcontr01.CRNETTOF, tbcontr01.CRNETTO, tbcontr01.CRIMPOSF, tbcontr01.CRIMPOS, tbcontr01.CRTOTALF, tbcontr01.CRTOTAL, tbcontr01.ANRAGSOC, tbcontr01.FZDESC, tbcontr01.RMDESC, tbcontr01.DRDESC, tbcontr01.Compagnia, tbcontr01.CRLORDO, tbcontr01.CRLORDOA, tbcontr01.CRNETTOA, tbcontr01.ProvvAnn, tbcontr01.VETARGA, tbcontr01.TS
FROM tbcontr01
WHERE (((tbcontr01.CODCOMP) Like comp) AND ((tbcontr01.RMID) Like ramo) AND ((tbcontr01.CPKUSID) Like ope) AND ((tbcontr01.USID) Like contr))
GROUP BY tbcontr01.CRID, tbcontr01.CRTIMEST, tbcontr01.CRNUM, tbcontr01.CRKRIID, tbcontr01.CRKSTID, tbcontr01.CRDECOR, tbcontr01.CRKFZID, tbcontr01.CRSCAD, tbcontr01.CRSRATA, tbcontr01.CRDFIRMA, tbcontr01.CRDSTAT, tbcontr01.CRNTAC, tbcontr01.CRPOLIE, tbcontr01.CRRATEO, tbcontr01.CRPROVVF, tbcontr01.CRPROVV, tbcontr01.CRCARAT, tbcontr01.CRSPEC, tbcontr01.CRMORA, tbcontr01.CRDANN, tbcontr01.CRDSOSP, tbcontr01.CRKCANID, tbcontr01.CRNETTOF, tbcontr01.CRNETTO, tbcontr01.CRIMPOSF, tbcontr01.CRIMPOS, tbcontr01.CRTOTALF, tbcontr01.CRTOTAL, tbcontr01.ANRAGSOC, tbcontr01.FZDESC, tbcontr01.RMDESC, tbcontr01.DRDESC, tbcontr01.Compagnia, tbcontr01.CRLORDO, tbcontr01.CRLORDOA, tbcontr01.CRNETTOA, tbcontr01.ProvvAnn, tbcontr01.VETARGA, tbcontr01.TS
            HAVING (((tbcontr01.CRKRIID) Like risc) AND ((tbcontr01.CRKSTID) Like stato) AND (vrData Between data1 And data2));
END

potete aiutarmi..?

Grazie
Matteo