Boolean to check group if there is 2 exact same values directly after ach other

I am grouping in Crystal reports and have a field that I am trying to monitor for 2 duplicated values should they follow directly after another at any time. Pleas开发者_StackOverflowe see example below :

IDTAG#14567 {Groupname}
Date              Device   Tagtype  MovementType  Firstname
01/01/11 08:15am  Entry     AVI         0         AnnaAVI1
01/01/11 08:25am  Entry     AVI         0         AnnaAVI2
01/01/11 11:35am  Exit      AVI         4         AnnaAVI2
01/01/11 12:05pm  Entry     AVI         0         AnnaAVI1
01/01/11 15:24pm  Exit      AVI         4         AnnaAVI1
01/01/11 16:00pm  Exit      AVI         4         AnnaAVI2

I need a 'True' value output only if {MovementType} has 2 value's of '0' followed in direct succession, it doesn't matter when it happens within the group.

To get the duplicate part, a formula that would accomplish it would be

previous({table.movementType}) = {table.movementType}

However then the problem is how to indicate that there were duplicates in a group regardless of where it occurred.

I haven't found a way to deal with that.