restrict collection to text values only

I have a list of entries that contain many instances of both numeric and text value that I am trying to restrict to text only (I dont need and items beginning with a number). This code gives me an output in column H of unique entries.

How can I use an If statement to filter only the entries starting with a letter??

Private Sub SubContractors()

Dim rng As Range
With Sheets("Sheet1")
Lrow = .Range("a" & Rows.Count).End(xlUp).Row
Set rng = .Range("a2:a" & Lrow)

    vaData = rng

    Set colUnique = New Collection
    
    For i = LBound(vaData, 1) To UBound(vaData, 1)

        On Error Resume Next
            colUnique.Add vaData(i, 1), CStr(vaData(i, 1))

        On Error GoTo 0
    Next i
    ReDim aOutput(1 To colUnique.Count, 1 To 1)
    For i = 1 To colUnique.Count
        aOutput(i, 1) = colUnique.Item(i)
    Next i
    .Range("h2").Resize(UBound(aOutput, 1), UBound(aOutput, 2)).Value = aOutput
    
    End With
End Sub