You could maybe use COUNTIFS
with the conditional formatting:
=COUNTIFS(D:D,D1,B:B,"<="&C1,C:C,">="&B1)>1
This counts all the instances where the following conditions are satisfied:
The responsible person is the same person (
D:D, D1
part)The dates the other activities begin are before or equal to the date a certain activity ends. (
B:B,"<="&C1
part)The dates the other activities end are equal or after to the date a certain activity begins. (
C:C,">="&B1
part)
The formula can make Excel respond quite slowly since it takes into consideration the whole column. Change it to a range if possible, for example, if you always have about 100 activities, you could maybe use:
=COUNTIFS(D1:D120,D1,B1:B120,"<="&C1,C1:C120,">="&B1)>1
Here is what I get after using this conditional formatting:
COUNTIFS
returns a number; a count of cells that satisfies the conditions. Since we have >1
at the end, this means that the cell(s) will get highlighted if there is more than one cell with the same conditions.