ABZBB

A x 1
B x 3
Z x 1

   Sub Macro1()
Dim Box As Shape
Set Box = ActiveDocument.Shapes.AddTextbox( _
Orientation:=msoTextOrientationHorizontal, _
Left:=50, Top:=50, Width:=200, Height:=400)
Box.TextFrame.TextRange.Text = "My text comes this way" + Chr(10)
Dim s As String
Application.ScreenUpdating = False
docLength = ActiveDocument.Range.Characters.Count

Box.TextFrame.TextRange.Text = Box.TextFrame.TextRange.Text + "Text length is: " + Str(docLength) + Chr(10)

Dim arr(128) As Integer
Dim character As Integer
For i = 1 To docLength - 1

        character = Asc(ActiveDocument.Range.Characters(i))
If iAsc >= 0 And iAsc <= 127 Then
         arr(character) = arr(character) + 1
 End If
Next i


End Sub

Sub CountChars()
    Dim iCount(57) As Integer
    Dim x As Integer
    Dim iTotal As Integer
    Dim iAsc As Integer

    Application.ScreenUpdating = False
    iTotal = ActiveDocument.Range.Characters.Count

    For x = 1 To iTotal
        iAsc = Asc(ActiveDocument.Range.Characters(x))
        If iAsc >= 65 And iAsc <= 122 Then
        iCount(iAsc - 65) = iCount(iAsc - 65) + 1
        End If
    Next x
    For x = 0 To 57
        Debug.Print x, iCount(x)
    Next x
    Application.ScreenUpdating = True
End Sub

Debug.Print Chr(x + 65), iCount(x)

'Tools, References: Microsoft Scripting Runtime
Sub CountCharsWithReplace()
    Dim doc As Document
    Dim rDupe As Range
    Dim dicChars As Scripting.Dictionary
    Dim s As String
    Dim iTotalChars As Integer
    Dim iTempChars As Integer
    Dim iDiff As Integer
    Dim n As Integer
    Dim blnExec As Boolean
    Dim lett As Variant
    Application.ScreenUpdating = False
    Set doc = ActiveDocument
    iTotalChars = doc.Range.Characters.Count
    Set rDupe = doc.Range
    Set dicChars = New Scripting.Dictionary
    Do While rDupe.Characters.Count > 1
        s = rDupe.Characters(1).Text
        blnExec = rDupe.Find.Execute(s, , , , , , , , , "", wdReplaceAll)
        iTempChars = doc.Range.Characters.Count
        iDiff = iTotalChars - iTempChars
        iTotalChars = iTempChars
        If Asc(s) >= 65 And Asc(s) <= 122 Then
            dicChars.Add s, iDiff
        End If
        n = n + 1
    Loop
    ActiveDocument.Undo Times:=n
    Application.ScreenUpdating = True
    For Each lett In dicChars.Keys
        Debug.Print lett, dicChars(lett)
    Next lett
End Sub

ActiveDocument.Range.ComputeStatistics(wdStatisticCharacters)

Activedocument.Range.Characters.Count

Selection.Range.ComputeStatistics(wdStatisticCharacters)

Selection.Range.Characters.Count

Function GetCharCountLoop(doc As Word.Document, char As String) As Long
Dim i As Long
Dim CharCount As Long

With doc.Content.Characters
    For i = 1 To .Count
        If .Item(i) = char Then
            CharCount = CharCount + 1
        End If
    Next i
End With
GetCharCountLoop = CharCount
End Function

Function GetCharCountFind(doc As Word.Document, char As String) As Long
Dim i As Long
Dim CharCount As Long

With doc.Content.Find
    Do While .Execute(FindText:=char, Forward:=True, MatchWholeWord:=False, MatchCase:=True) = True
        CharCount = CharCount + 1
    Loop
    GetCharCountFind = CharCount
End With
End Function

Function GetCharCountString(doc As Word.Document, char As String) As Long
Dim chars As String
Dim i As Long
Dim CharCount As Long

chars = doc.Content
For i = 1 To Len(chars)
    If Mid$(chars, i, 1) = char Then
            CharCount = CharCount + 1
        End If
    Next i
GetCharCountString = CharCount
End Function

Function GetCharCountRegex(doc As Word.Document, char As String) As Long
Dim chars As String
Dim CharCount As Long
Dim objRegExp As Object

chars = doc.Content
Set objRegExp = CreateObject("VBScript.RegExp")
With objRegExp
    .Pattern = char
    .IgnoreCase = False
    .Global = True
    CharCount = .Execute(chars).Count
End With
GetCharCountRegex = CharCount
End Function

Sub TimeMethods()
Dim char As String
Dim CharCount As Long
Dim LoopCounter As Long
Dim NumLoops As Long
Dim StartTime As Double

char = "a"
NumLoops = 1

StartTime = Timer
For LoopCounter = 1 To NumLoops
CharCount = GetCharCountLoop(ActiveDocument, char)
Next LoopCounter
Debug.Print CharCount
Debug.Print Timer - StartTime

StartTime = Timer
For LoopCounter = 1 To NumLoops
CharCount = GetCharCountFind(ActiveDocument, char)
Next LoopCounter
Debug.Print CharCount
Debug.Print Timer - StartTime

StartTime = Timer
For LoopCounter = 1 To NumLoops
CharCount = GetCharCountString(ActiveDocument, char)
Next LoopCounter
Debug.Print CharCount
Debug.Print Timer - StartTime

StartTime = Timer
For LoopCounter = 1 To NumLoops
CharCount = GetCharCountRegex(ActiveDocument, char)
Next LoopCounter
Debug.Print CharCount
Debug.Print Timer - StartTime

End Sub