I'm using the custom "SortConcat" function from Jelen and Syrstad's "VBA and Macros for Microsoft Excel." 

Function SortConcat(Rng As Range) As Variant 
 Dim MySum As String, arr1() As String 
 Dim j As Integer, i As Integer 
 Dim cl As Range 
 Dim concat As Variant 
 On Error GoTo FuncFail: 
 'initialize output 
 SortConcat = 0# 
 'avoid user issues 
 If Rng.Count = 0 Then Exit Function 
 'get range into variant variable holding array 
 ReDim arr1(1 To Rng.Count) 
 'fill array 
 i = 1 
 For Each cl In Rng 
     arr1(i) = cl.Value 
     i = i + 1 
 Next 
 'sort array elements 
 Call BubbleSort(arr1) 
 'create string from array elements 
 For j = UBound(arr1) To 1 Step -1 
     If Not IsEmpty(arr1(j)) Then 
         MySum = arr1(j) & ", " & MySum 
     End If 
 Next j 
 'assign value to function 
 SortConcat = Left(MySum, Len(MySum) - 2) 
 'exit point 
 concat_exit: 
 Exit Function 
 'display error n cell 
 FuncFail: 
 SortConcat = Err.Number & " - " & Err.Description 
 Resume concat_exit 
 End Function 
 
Sub BubbleSort(List() As String) 
 'Sorts the List array ascending order 
 Dim First As Integer, Last As Integer 
 Dim i As Integer, j As Integer 
 Dim Temp 
 First = LBound(List) 
 Last = UBound(List) 
 For i = First To Last - 1 
     For j = i + 1 To Last 
         If UCase(List(i)) > UCase(List(j)) Then 
             Temp = List(j) 
             List(j) = List(i) 
             List(i) = Temp 
         End If 
     Next j 
 Next i 
 End Sub

The issue is that I want to concatenate only the data in a given column that correspond to a value in another column. You could say, for example, that I have a list of names in column A, and I want to concatenate those names that have the text "this one!" appearing next to them in column B.

Sorry if I'm violating copywright. "VBA and Macros for Microsoft Excel" is a great book, and I recommend that everyone buy it. : )

Cross-posted from mrexcel.com, where I got 0 responses. Sample worksheet attached.