Access Query question

I currently have a query that pulls the info I need form other queries. Here's the query:

 

SELECT Employee.EmpName, Matter.MatFeeFreqCode, Matter.MatExpFreqCode, Format([Client.CliCode],"0000") AS CliCode, Client.CliReportingName, Matter.MatReportingName, Format([Matter.MatCode],"0000") AS MatCode, Matter.MatDateLastBill, Matter.MatDateLastPaymt, Matter.MatDateOpened, Matter.MatBillAgreeCode, Sum(GWB_WIP_AR_FEE_EXP_UNION.SumOfUTAmount) AS UnbilledTime, Sum(GWB_WIP_AR_FEE_EXP_UNION.SumOfUEAmount) AS UnbilledExpenses, Sum(GWB_WIP_AR_FEE_EXP_UNION.ARFee) AS FeesAR, Sum(GWB_WIP_AR_FEE_EXP_UNION.ARExp) AS ExpAR, Employee.Group, Matter.MatBillMonth, Matter.MatBillCycle
FROM GWB_WIP_AR_FEE_EXP_UNION INNER JOIN (Employee INNER JOIN ((Client INNER JOIN Matter ON Client.CliSysNbr = Matter.MatCliNbr) INNER JOIN BillTo ON Matter.MatBillTo = BillTo.BillToSysNbr) ON Employee.EmpSysNbr = BillTo.BillToBillingAtty) ON GWB_WIP_AR_FEE_EXP_UNION.SysNum = Matter.MatSysNbr
GROUP BY Employee.EmpName, Matter.MatFeeFreqCode, Matter.MatExpFreqCode, Format([Client.CliCode],"0000"), Client.CliReportingName, Matter.MatReportingName, Format([Matter.MatCode],"0000"), Matter.MatDateLastBill, Matter.MatDateLastPaymt, Matter.MatDateOpened, Matter.MatBillAgreeCode, Employee.Group, Matter.MatBillMonth, Matter.MatBillCycle
ORDER BY Employee.EmpName;

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The MatFeeFreq Code only returns M, Q, or C. The MatBillMonth and MatBillCycle returns numbers. I need to create another field on the fly call Freq that will concatenate MatFreqCode with either the MatBillMonth or the MatBillCycle depending on what the value of the freq code is. These three fields are straight out of the Matter table.

I have tried this but it didnt work:

IIf([MatFeeFreqCode]="M","[MatFeeFreqCode]",IIf([MatFeeFreqCode]="C",[MatFeeFreqCode]&[MatBillCycle],[MatFeeFreqCode]&[MatBillMonth]

What I am trying to accomplish is another field called Freq that has the freq code and the either the cycle nymber or the month number depending on the value of the freq code.

Thanks