Countif backwards and autofill forward

[Mistert271828]

Hey. I am trying to figure out a formula that will countif backwards until 3 cells have been counted with various blank cells in between that I can autofill forward that will always just countif the most recent (from right to left) 3 cells. The if of the countif is just >=3.

W1	W2	W3	W4	W5	W6	W7	W8	W9	W10
	1		3			2		5
									formula here that i can autofill forward

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So where the formula is in the table would return 2 and only count back to W4.

Thanks for the help!