Regex extract data before certain text - regex

Question

I have large text documents that has some data I want to be extracted.
As you can see in a screenshot , I want to extract A040 to excel column next to the filename.
Before the A040 there is always three empty spaces and than text Sheet (also in screenshot)
Every file has different number and there is always letter A with three digits and text Sheet. --> example file uploaded:
I has something already in VB with Excel but it is not working.
Dim cell As Range
Dim rng As Range
Dim output As String
Set rng = ws.Range("A1", ws.Range("A1").SpecialCells(xlLastCell).Address)
For Each cell In rng
On Error Resume Next
output = ExtA(cell.Value)
If Len(output) > 0 Then
Range("B" & j) = output
Exit For
End If
Next
j = j + 1
ws.Cells.ClearContents
'Call DelConns
strFileName = Dir 'next file
Loop
End Sub
Function ExtA(ByVal text As String) As String
'REGEX Match VBA in excel
Dim result As String
Dim allMatches As Object
Dim RE As Object
Set RE = CreateObject("vbscript.regexp")
RE.Pattern = "(?<=Sheet)[^Sheet]*\ Sheet"
RE.Global = True
RE.IgnoreCase = True
Set allMatches = RE.Execute(text)
If allMatches.Count <> 0 Then
result = allMatches.Item(0).submatches.Item(0)
End If
ExtA = result
End Function

Answer 1

This seems to work on your sample.
Option Explicit
Function AthreeDigits(str As String)
Dim n As Long, nums() As Variant
Static rgx As Object, cmat As Object
'with rgx as static, it only has to be created once; beneficial when filling a long column with this UDF
If rgx Is Nothing Then
Set rgx = CreateObject("VBScript.RegExp")
Else
Set cmat = Nothing
End If
AthreeDigits = vbNullString
With rgx
.Global = False
.MultiLine = True
.Pattern = "\A[0-9]{3}[\s]{3}Sheet"
If .Test(str) Then
Set cmat = .Execute(str)
AthreeDigits = Left(cmat.Item(0), 4)
End If
End With
End Function

Answer 2

Did you mean to say that there are 4 spaces after the A040 and before the "Sheet"? If so, try this pattern:
.pattern = "(A\d\d\d)\s{3}Sheet"
EDIT: I thought you said 4 spaces, but you said 3. My pattern now reflects that.
EDIT 2: (I need more coffee!) Change the \b to \s.

Answer 3

See Example here
"\s+[Aa]\d*\s+Sheet"
Or
\s+[Aa]\d*\s+(Sheet)
Or
[Aa]\d*\s+(Sheet)
Demo
https://regex101.com/r/Qo8iUf/3
\s+ Matches any whitespace character (equal to [\r\n\t\f\v ])
+ Quantifier — Matches between one and unlimited times, as many times as possible
Aa Matches a single character in the list Aa (case sensitive)
\d* Matches a digit (equal to [0-9])
* Quantifier — Matches between zero and unlimited times, as many times as possible