Thank you both for your help 
I used this code to get what I wanted, but will have to repeat it many times with other cost centres to capture all the data:
DateNow = Date
FromDate = DateSerial(Year(DateNow), Month(DateNow), 1): ToDate = DateSerial(Year(DateNow), Month(DateNow) + 1, 0)
InMonth = FormatCurrency(Application.WorksheetFunction.SumIfs(.Range("J:J"), _
.Range("P:P"), GLCode, _
.Range("L:L"), ">=" & FromDate, _
.Range("L:L"), "<" & ToDate, _
.Range("Z:Z"), "MasterFile_00") + _
Application.WorksheetFunction.SumIfs(.Range("J:J"), _
.Range("P:P"), GLCode, _
.Range("L:L"), ">=" & FromDate, _
.Range("L:L"), "<" & ToDate, _
.Range("Z:Z"), "MasterFile_01"))
Debraj Roy, your formulae has increased my knowledge in using arrays. Thanks
oeldere, thanks for showing how to create a pivot table using VBA. I will probably use that approach rather than using my code.
Cheers
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