Need to calculate a total from a range of cells on different sheets

Hello,
I am new to this, so i appreciate your patience and help in advance! I have a file that I need to have PTO hours calculated. I have attached the file.
Basically, people (joe, susy, griffin, tom, etc) will enter their PTO hours in the month and day that they will be taking it. There will be seperate sheets for each month of the year (my file currently only has July and August). I want the total PTO hours per person added together and seen on a seperate sheet within the workbook (PTO_Totals).
I have tried several nested IF formulas that ended up being too cumbersome, and I don't know enough about VBE to create a macro.
Please help. Thank you!

Sample.xlsx