An expression ike
IF(COUNT(C1:I1)=4,SUM(LARGE(C1:I1,{1,2,3,4} means there are only 4 numbers in the range, so, why the LARGE function?
As I understand it

=IF(count(C1:I1)>=5,sum(large(C1:I1,{1,2,3,4,5})), sum(c1:I1))

should do?

(entered as array of course)

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