I would like to request some help, in creating macro which can read data from one/or more sheet and copy and paste it into another sheet, by matching up column A & B and Row 1, between the both sheets.

I have monthly data stored in each sheet, named as May, June, July etc. I also have sheet called 'monthly' within the same workbook, where I would like to extract all monthly totals, from sheets july, June etc, into the 'Monthly' worksheet by matching up its names from Column A and B and row1 header with each sheet's names.

The june,july worksheets have date1, date2 etc, columns with data and after those columns, there are the 'bs, rm, cm, cd, cl' columns, and these are the columns, I would like to use, to extract the numbers from and paste in the 'monthly' worksheet.

My current issue, is that the 'bs, rm, cm..etc' columns are not fixed, due to the 'date1, date2 etc' columns can vary, for each month.

For this current task, I was using a formula as shown below to extract the values into 'monthly' worksheet, however due to unfixed columns for 'bs, rm, cm... etc', I could not get the formula to work for the 'july' and 'Aug' months (i.e. extract data into 'monthly' worksheet, from the june&aug sheets). 
=IFERROR(SUMIFS(OFFSET(INDIRECT(C$1 & "!$A$3:$A$21"),0,MATCH($A3,INDIRECT(C$1 & "!$A$1:$G$1"),0)-1),INDIRECT(C$1 & "!$A$3:$A$21"),$A3,INDIRECT(C1 & "!$B$3:$B$21"),$B3),"")
I would like to request, if it is possible to use the formula below to re-create macro which can carry out this task, by extracting all the values from 'june, july, aug etc' sheet, into the 'monthly' sheet, at once.

I have attached a sample workbook with example of data layout and desired output shown in monthly worksheet.
data_extraction2.xls

I hope i have explained my issue clearly, if not, then please free to ask further question, for any clarification.

Thank you, for all your help.