relation of more than one column watched by change timestamp

[kevin_mjc]

If I have a change timestamp that set to watch more than one column, how would they trigger the change timestamp?
Example :
Watched column : A , B, C
Which one of this will happen :
1.  The change in A or B or C will trigger the change timestamp
2. The change in A and B and C together will trigger the change timestamp

[Suvrutt_Gurjar]

It is option 1 you described.

[kevin_mjc]

So, if I would like to have the change timestamp triggered only after column A dan B and C change altogether, what should I do?

[Suvrutt_Gurjar]

One option to try will be to create a datetime type column instead of ChangeTimestamp column.

For this datetime type column,  please have an app formula expression of 

IF(AND([_THISROW_BEFORE].[Column A]<>[Column A], [_THISROW_BEFORE].[Column B]<>[Column B], [_THISROW_BEFORE].[Column C]<>[Column C]),NOW(),[_THIS])

Please leave initial value as blank for this column. Please test well.

[AleksiAlkio]

Option #1 with OR()