Time = 
IF(
    NOT(ISBLANK(Sheet1[Start Date])) &&
    NOT(ISBLANK(Sheet1[End Date])),
    NETWORKDAYS(
        Sheet1[Start Date],
        Sheet1[End Date],
        IF(
            OR(
                Sheet1[Country Name] = "Saudi Arabia",
                Sheet1[Country Name] = "Egypt"
            ),
            7,
            1
        )
    ) - 1,
    BLANK()
)