Macro to extract numbers freezes excel

Standard disclaimer: I'm not a VBA regular. I rarely work with Excel so most of my code is gleaned from more qualified folks, hopefully like you.

I'm writing a macro (or a series of them which I'll combine later) to calculate a due date based on invoice date and terms (expressed as NET10). Everything is running well except this critical part of extracting the numerical value. This code is beyond me once it gets to the InputBox which I'd be happy to replace with a selection of a specific column since it will always be the same one.

It works... eventually. When running this macro excel goes into a (not responding) state for a period of several minutes before pushing out the results. The results are correct but I can't explain why it struggles, my cpu doesn't exceed 20% so it's not lack of processor power.

So my question is twofold:
Can this be written in a way that doesn't bog down excel?
and
Is it possible to replace the selection with an assigned selection like something that is working in other sections: Range("D1:D" & LastRow)
(yes, I would have to declare LastRow Variable)

Sub GetNumbers()
    Dim xRegEx As Object
    Dim xRg As Range
    Dim xCell As Range
    Dim xTxt As String
    On Error Resume Next
    xTxt = ActiveWindow.RangeSelection.Address
    Set xRg = Application.InputBox("please select range:", "Test", xTxt, , , , , 8)
    If xRg Is Nothing Then Exit Sub
    Set xRegEx = CreateObject("VBScript.RegExp")
    With xRegEx
        .Pattern = "\D+"
        .IgnoreCase = True
        .Global = True
    End With
    xRg.NumberFormat = "General"
    For Each xCell In xRg
        xCell.Value = xRegEx.Replace(xCell.Value, "")
    Next
    Set xRegEx = Nothing
End Sub

while I have the floor, one more question:
Is it better to write multiple macros and call them in a single one or actually write them as one?

Thanks for this forum helping get me this far.

Thanks for confirming my instinct.

I don't even like regex in php, the lag is really annoying but eliminating the InputBox will make this a lot better on the end user.

Originally Posted by shg

You're not selecting entire columns, are you?

Well that explains why it takes so long...

That means the more important question is how can I select only to the last row without using an InputBox?
If nothing else, you have proven once again that my biggest problems are never what they seem.

Thanks shg but it didn't take long to realize I'm not nearly well versed enough to put that into context.

If, using the GetNumbers() function as I posted, how would this replace the selection step considering I need to select the contents of column E?
And that without selecting the entire column of cells as you pointed out.