FileMaker Pro Custom Functions

/* AddRemoveListItems (theList; theValues) Adapted from function by: David Head, uLearnIT theList: standard return separated list theValues: text This function will add an item to a list if it does not already exist; otherwise the item is removed from the list Always removes empty lines from list, including leading/trailing returns Simply remove empty lines from list: AddRemoveListItems ( theList; "") Recursive: theValues can be a list of values Each will be processed in sequence By Bruce Robertson 6/19/10 V 1.01 */ Let ([ LV = ValueCount( theValues); thisValue= GetValue( theValues; 1); moreValues = MiddleValues( theValues ; 2; ValueCount( theValues)); novalue = IsEmpty ( FilterValues ( theList ; thisValue ) ); newList = Substitute( theList; ["¶¶¶"; "¶"] ; ["¶¶"; "¶"] ) ; listminusvalue = Substitute( "¶¶" & newList & "¶¶"; [¶ & thisValue & ¶ ; ¶ ] ; ["¶¶¶"; ""] ; ["¶¶"; ""] ) ; listplusvalue = Substitute( List ( newList ; thisValue ); ["¶¶"; "¶"] ); result = Case ( novalue ; listplusvalue ; listminusvalue ); LNR = Length( result ); TR = Right( result; 1) = "¶"; LR = Left ( result; 1) = "¶"; result = Middle ( result; 1+ LR; LNR - TR - LR ) ]; Case( LV < 2 ; result; AddRemoveListItems( result; moreValues) ) )
 Then copy & paste into FileMaker Advanced's Edit Custom Function window.