Alter a value based on day of week?

[wasafiri]

Hi, any idea how to alter a value based on the day of the week?

Basically I need a formula that says the following:

If it's Monday average L40 and I4, and multiply it by M34
If it's Tuesday average L40 and I4, and multiply it by M35
If it's Wednesday average L40 and I4, and multiply it by M36
If it's Thursday average L40 and I4, and multiply it by M37
If it's Friday average L40 and I4, and multiply it by M38
If it's Saturday average L40 and I4, and multiply it by M39
If it's Sunday average L40 and I4, and multiply it by M40

Ideas??? I'm a bit stumped! It'd be an awfully loooooong expression, whatever it ends up being. Thanks in advance!