Variables inside a formula

Hi Guys,
I hope you are all doing well. I have a query and I would like your help on that.

I have 30 excel spreadsheets named 15-Jun.xls,16-Jun.xls,17-Jun.xls....etc. I have lots of data in these. Now I have another spreadsheet Month_of_June.xls. I am using COUNTIF to evaluate some columns in the spreadsheets for each day of the month.

I have a formula in Month_of_June.xls which is something like

=COUNTIF('J:\Harish\Analytics\[15-Jun.xls]15-Jun'!$D$4:$D$133,"Harish Kumar")

Now when I drag, I want it to become something like this

COUNTIF('J:\Harish\Analytics\[15-Jun.xls]15-Jun'!$D$4:$D$133,"Harish Kumar")
COUNTIF('J:\Harish\Analytics\[16-Jun.xls]15-Jun'!$D$4:$D$133,"Harish Kumar")
COUNTIF('J:\Harish\Analytics\[17-Jun.xls]15-Jun'!$D$4:$D$133,"Harish Kumar")
COUNTIF('J:\Harish\Analytics\[18-Jun.xls]15-Jun'!$D$4:$D$133,"Harish Kumar")

Only the date should change. The spreadsheet name should change. Is there some method of getting this done?