EARLY or LATE based on two fields in Accsess.

I've asked this question before and it was solved but wanted to add another criteria to the same question.   I have this sql statement in Access and what I wanted to do is add a field that would read "EARLY" if the number is negative and "LATE" if the number is positive based on  the "DAYS_LATE" field which is a numerical field .  

This was theanswer:
ON-TIME: IIf(DateDiff("d",[CONF_DEL_DATE],[REC_DATE])<=0,"EARLY","LATE")    

My question now is can "EARLY" "LATE" be done against two fields.  Basically REC_DATE first looks at CONF_DEL_DATE and tells me if it's either EARLY or LATE but if it's blank then look at the date of PLN_DEL_DATE to tell me if it's EARLY or LATE.   Can this be done?  See Below SQL Statement......

SELECT DISTINCT tbl_PO_REC.PO, tbl_PO_REC.POS, tbl_PO_REC.SUPP_NO, tbl_PO_REC.SUPP_NAME, tbl_PO_REC.ITEM, tbl_PO_REC.REC_NO, tbl_PO_REC.ORD_QTY, tbl_PO_REC.DEL_QTY, tbl_PO_REC.BACK_ORD_QTY, tbl_PO_REC.TOTAL_COST, tbl_PO_ALL.ORD_DATE, tbl_PO_ALL.PLN_DEL_DATE, tbl_PO_ALL.CONF_DEL_DATE, tbl_PO_REC.REC_DATE, DateDiff("w",[ORD_DATE],[REC_DATE]) AS LEAD_TIME_IN_WKS, DateDiff("d",[PLN_DEL_DATE],[REC_DATE]) AS DAYS_LATE, IIf(DateDiff("d",[CONF_DEL_DATE],[REC_DATE])<=0,"EARLY","LATE") AS [ON-TIME]
FROM tbl_PO_REC LEFT JOIN tbl_PO_ALL ON (tbl_PO_REC.POS = tbl_PO_ALL.POS) AND (tbl_PO_REC.PO = tbl_PO_ALL.PO)
WHERE (((tbl_PO_REC.SUPP_NO)<>59944 And (tbl_PO_REC.SUPP_NO)<>16106 And (tbl_PO_REC.SUPP_NO)<>25278 And (tbl_PO_REC.SUPP_NO)<>27001 And (tbl_PO_REC.SUPP_NO)<>36607 And (tbl_PO_REC.SUPP_NO)<>58663 And (tbl_PO_REC.SUPP_NO)<>92017) AND ((tbl_PO_REC.ITEM)<>"COST ITEM") AND ((tbl_PO_REC.REC_DATE) Is Null Or (tbl_PO_REC.REC_DATE)>#12/31/2018#))
ORDER BY tbl_PO_REC.REC_DATE DESC;