Flagging low quantities by groups

Hi Friends,

I need help creating a formula for a work problem. I work for a clothing company as a analyst and need to set up a formula that tells me when inventory in a store for a certain article of clothing (An article is a model in a certain colour) is sitting below 3 units. ideally, the formula (or a seperate one) could also flag when there isn't 2 out of 3 core sizes remaining per article (the core sizes are S, M, and L)

So for example, from the attached sheet. I would want the formula to flag the "Phase SL bottom men's black" because it only has 2 units in store. I would also want to flag the "phase SL boxer men's black" because even though it has 8 units it doesn't have any of the core sizes.

If anyone is able to help me solve this, I will be forever grateful! I've been trying different things and haven't figured it out for months now.

I've attached a small example of the inventory but they usually get to be over 4000 lines or more. Here's a rough if you can't see the attachment:

Model_Color SizeCode Sum of Quantity On Hand
Phase AR Bottom Women's Black L 2
Phase AR Bottom Women's Black M 1
Phase AR Bottom Women's Black S 3
Phase AR Bottom Women's Black XL 1
Phase AR Bottom Women's Black XS 2
Satoro AR Bottom Women's Black L 3
Satoro AR Bottom Women's Black M 1
Satoro AR Bottom Women's Black S 1
Satoro AR Bottom Women's Black XL 1
Phase SL Bottom Men's Black L 1
Phase SL Bottom Men's Black M 1
Phase SL Boxer Men's Black XL 4
Phase SL Boxer Men's Black XS 3
Phase SL Boxer Men's Black XXL 1

Thank you so much Malvosh! I tried the formula but for some reason it isn't highlighting properly for me. It's highlighting the last of an article but it's not even doing it correctly, it's highlighting articles that have more than 3 units in the file.

Would you be able to take a look at the attached file that I worked on? The format is a little different but the idea is exactly the same.

You are the man! I was able to get the first part with the "sumif" formula working and put it into the Macro I'm building.

I have a question about the second formula with the "countifs". I was hoping to put in a conditional formatting formula that highlights when an article has less than 2 of the core sizes (S,M,L) with inventory in the store. For example, the first article that you see in the attached list is the "Alpha AR pant men'sPilot". It has 5 units total in store but 4 of those units are only in the "XL" size and 1 unit is in size "S". This is a situation where it would be great to have this flagged because it doesn't meet the requirement of 2/3 of the core sizes (S,M,L) having inventory.
Is there a conditional formatting formula you can think of that would highlight this situation?

Thank you soooooooooooooo much again for your help.

I've attached the example I'm referring to.

You are a god among men! What a hero. Thank you Melvosh