While SUM itself doesn't directly differentiate between weekdays and weekends, you can combine it with other functions in Excel to achieve this. Here are two methods:

Method 1: Using SUM and WEEKDAY functions

1. Weekday Identification: Create a helper column (e.g., Column C) to identify weekdays (1) and weekends (0) using the WEEKDAY function. In cell C2, enter the formula `=WEEKDAY(A2,2)`. 2 indicates Monday as the first day of the week. Adjust this number if your week starts on a different day (1 for Sunday).
- Drag the formula down to apply it to all your data rows.

2. Conditional SUM: Use SUM with an IF statement to conditionally add values based on weekdays:
In another cell (e.g., D2), enter the formula:
`=SUMIF(C2:C$10, 1, A2:A$10)` (Replace ranges based on your data location)
- This formula instructs SUM to look at the weekday identifications in C2:C10 (adjust the range as needed).
- It adds corresponding values in A2:A10 (data range) only if the weekday identification is 1 (weekday).

Method 2: Using SUMIFS and a Weekend Helper Column

1. Weekend Identification: Create a helper column (e.g., Column C) to identify weekends with TRUE/FALSE values. In cell C2, enter the formula `=OR(WEEKDAY(A2,2)=1, WEEKDAY(A2,2)=7)`. This identifies Saturdays (7) and Sundays (1) as TRUE (weekend).
- Drag the formula down to apply it to all your data rows.

2. Conditional SUM: Use SUMIFS to add values based on weekdays:
In another cell (e.g., D2), enter the formula:
`=SUMIFS(A2:A$10, C2:C$10, FALSE)` (Replace ranges based on your data location)
- This formula instructs SUMIFS to look at the data range (A2:A10) and the weekend identification range (C2:C10).
- It adds corresponding values in A2:A10 only if the weekend identification is FALSE (weekday).

Remember to adjust the cell ranges in the formulas based on your actual data location.

Both methods achieve the same result: calculating the sum considering only weekdays or weekends based on your choice. Choose the method that best suits your needs and data structure.