How to take formula inputs to a UDF like conditional formatting
问题 Imagine you want to check whether the left letter of each word in a range is "a", then join the words for which that condition is true. One way is with a helper column, returning "" if not true, the word if it begins with "a", and then a total row which CONCAT() s over the helper column. Another way would be to use an array formula. {=CONCAT(IF(LEFT(range) = "a", range, ""))} . That's effectively using a helper column anyway. But what I want is to use the conditional formatting approach: When