Using INDIRECT to make index/match formula reference multiple worksheets in same workbook

Thanks - that has certainly taken care of the "REF!" error, but the value returned is incorrect. I changed the formula as you suggested and it returned 7/14/2016 instead of Schedule.xlsxSchedule.xlsx

Hi. I am new to this thread, but I have a similar issue and can't figure it out. I am indexing and matching two different defined rows in a worksheet. The Criteria is the volume amount and if it goes above a certain number, the month it occurred is when I want to hire someone. I have it working on one worksheet. The issue is how I add an indirect to look at each of the other worksheets. The formula is listed below. The sheet names are Operating Pan '17, Operating Plan '18...etc. Any help on this would be helpful.

=IFERROR(INDEX('Operating Plan ''17'!$D$2:$O$2,MATCH(INDEX('Operating Plan ''17'!$D$4:$O$4,MATCH(TRUE,'Operating Plan ''17'!$D$4:$O$4>=B28,0)),'Operating Plan ''17'!$D$4:$O$4,0)),"")