Creating a match index formula comparing two variables in two worksheets

I am trying to compare two different vlaues in two different columns in two different worksheets. If the values in both columns match it will result in a value of "Scheduled" by using the INDEX part of the formula. I have a formula for match index that I use often (see copy below), but it only matches one value in one colume. I can't figure out how to include another column/value to match.

=IF(ISNA(MATCH(C2,Main!$A:$A,0)),0,INDEX(SCHEDULE!$B:$B,MATCH(C2,Main!$A:$A$,0)))

There are three changes I want to make to this formula:

1. Match two values in two columns (one value in each column)

2. Instead of the Index returning a value from another column, return a value that I write into the formula. In this case, if the month values and the circuit values match in both worksheets, then return the value "Scheduled."

I also want to reference entire columns instead of specific row numbers in a column, hence the A:A designation instead of A2:A400 for example.

Thanks!

Here is a very basic and brief sample. Column F is where the formula will go and where if columns A and D in this Main worksheet match columns A and C in the SCHEDULED worksheet.

Thank you for this formula. I did have an issue with it though and want to see if you can help me. Please note that I only had to make one change to what you provided (changed the D2 to E2). However, when I put the formula in the cell and press "Enter," the window that you would see to save a new file opens automatically. It also returns blank values in the cells when it should show "Scheduled" as I validated this data part.

I have had this happen before, and usually I could fix it by fixing something in the formula, but I am not seeing where to fix anything with what you provided - looks pretty straight forward. Can you help me with this issue?

=IF(ISERROR(MATCH(A2&E2,INDEX(SCHEDULED!$C$1:$C$10000&SCHEDULED!$A$1:$A$10000,0),0)),"","Scheduled")