Create a formula in excel that deals with range of dates based on a certain value

Job ID: 31250578

Budget: $10 – $30 USD

I have an excel sheet that has 3 tabs:
1. 2021 safety enrollment courses (courses offers with dates and employee #)
2. 2021 UPDC courses (courses offers with dates and employee #)
3. 2021 GGPED vacation plan (main vacation & short leave)

I need to find if the (courses offers) in the sheet (1) and (2) dates are not in a conflict with (vacation) dates in sheet (3) based on the employee #