Summing across sheets but the range is based on dropdown?

I have a spreadsheet that sums up monthly sheets of information. I am trying to do a YTD calculation - for example =SUM('Jan19:Dec19'!A8). But, I have a dropdown list of months which are names of the sheets with data in the workbook.



I want to sum one cell across a range of sheets depending on what is selected in the dropdown list. For example, if I select Mar19, it adds A8 for January, February and March. I want to keep January as the first monthly sheet. I have tried using INDIRECT to refer to the dropdown list within my function but a #REF error keeps appearing. I have also tried just putting the cell # of the dropdown in place of 'Dec19'.



Is there any solution to this problem? Or is this even possible? If more clarification is needed I would be happy to provide it. Thanks.

Assuming your tab names list starts from M14 in your Summary tab and that the cell with desired value in each month tab is A8, create a list of values next to it (column N or any other free column) from each month cell like this, copied down:
N14=INDIRECT("'"&M14&"'!A8")
Assuming your drop-down cell is N13, create a named range Sheets, for example and in the “Refers to” field, paste this:
=OFFSET('Summary!$N$14,,,MATCH($N$13,$M$14:$M$25,0),1)
Then use this for your sum:
=SUM(Sheets)
Change ranges and tab names accordingly.