Same macro for multiple textboxes on the same userform excel vba

Simple example:

Add a new class module to your project and rename it NumericTextbox. Paste this code into it:

Option Explicit
Private WithEvents tb As MSForms.TextBox
Public Property Set TextControl(t As MSForms.TextBox)
    Set tb = t
End Property
Private Sub tb_Change()

    With tb

        If Not IsNumeric(.Value) And .Value <> vbNullString Then

            MsgBox "Sorry, only numbers allowed"

            .Value = vbNullString

        End If

    End With

End Sub

Now in your userform, add this code:

Option Explicit
Private colTBs                As Collection
Private Sub UserForm_Initialize()
    Dim ctl                   As MSForms.Control
    Dim oHandler              As NumericTextbox
    Set colTBs = New Collection

    For Each ctl In Me.Controls
        If TypeOf ctl Is MSForms.TextBox Then
            Set oHandler = New NumericTextbox
            Set oHandler.TextControl = ctl
            colTBs.Add oHandler
        End If
    Next ctl
End Sub

and there you go.

I just passed the textbox as an argument into my function as follows:

sheet code

Private Sub TextBox1_Change()

test Me.TextBox1

End Sub

Private Sub TextBox2_Change()

test Me.TextBox2

End Sub

Module code:

Sub test(textbox As Object)

    With textbox

        If Not IsNumeric(.Value) And .Value <> vbNullString Then

            MsgBox "Sorry, only numbers allowed"

            .Value = vbNullString

        End If

    End With

End Sub

The easy way would be to have a handler for each of the text boxes so that a particular procedure follows each individual action, I would suggest separating your procedure as the following

Private Sub checkValue()
With Me.ActiveControl
            If Not IsNumeric(.Value) And .Value <> vbNullString Then
                MsgBox "Sorry, only numbers allowed"
                .Value = vbNullString
            End If
        End With
End Sub

`Then call that sub from each of the textbox_change() procedures