excel vba keep only numbers in string

Question

I have this code that gets whatever is on the clipboard and removes several characters.
But recenty these characters also became alphacaracters too.
I came across this code that REMOVES the numbers but I want to is just simply keep ~only~ the numbers, its inverse.

I did a lot of googleing and could not figure it out.

    Dim x
    Dim tmp As String
    tmp = input1
    'remove numbers from 0 to 9 from input string
    For x = 0 To 9
        tmp = Replace(tmp, x, "")
    Next
    'return the result string
    removenumbers = tmp  

My current code does this:

Sub y_chave_danfe()

    On Error GoTo ER2

    Dim atransf As New MSForms.DataObject
    Dim chave As Variant
    Dim danfe As Variant

    atransf.GetFromClipboard
    chave = atransf.GetText
    danfe = Replace(Replace(Replace(Replace(Replace(chave, " ", ""), "/", ""), "-", ""), ".", ""), "_", "")
    CreateObject("htmlfile").parentWindow.clipboardData.setData "text", danfe

Exit Sub

ER2:
End Sub

Answer 1

A simple method is by using Regular Expressions in a function. Merely pass the string to this function, at it will remove all of the non-digits:

Function removeNonDigits(str As String) As String 'or as long, if you prefer
    Dim re As Object
    
Set re = CreateObject("vbscript.regexp")
With re
    .Pattern = "\D+"
    .Global = True
    removeNonDigits = .Replace(str, "")
End With
End Function

If you don't want to use Regular Expressions, you can loop through the string:

Function removeNonDigits(str As String) As String
    Dim I As Long
    Dim tmp As String

tmp = ""
For I = 1 To Len(str)
    If IsNumeric(Mid(str, I, 1)) Then
        tmp = tmp & Mid(str, I, 1)
    End If
Next I

removeNonDigits = tmp
End Function