Excel Userform: Populate other controls (i.e. textbox & combobox) based on combobox select

Hi There, I'm trying to create a userform that will allow one to select a subject from a combobox and populate the remaining controls with data from the corresponding spreadsheet. Here's the code I've been trying with no success:

Private Sub cboStudyID_Change()
    'populate data on userform based on StudyID selection
    Dim strNamedRange As String
    Dim lRelativeRow As Long
     
    With ComboBox1
        If .ListIndex > -1 Then
            strNamedRange = .RowSource
             'ListIndex starts at zero
            lRelativeRow = .ListIndex + 1
             'Fill with adjacent column to Combobox choice
            txtEnrollmentDate = Range(strNamedRange)(lRelativeRow, 2)
             'Fill with 2nd adjacent column to Combobox choice
            cboSite = Range(strNamedRange)(lRelativeRow, 3)
             'Fill with 3rd adjacent column to Combobox choice
            cboRetention = Range(strNamedRange)(lRelativeRow, 4)
        End If
    End With
    

End Sub

Attached is a simplified version of the .xlsm I'm working with....Any suggestions on how to make this work?