Group number sequence inside a range - excel

Question

I am new to VBA and learning myself...
I am facing a similar problem with this post: Excel Vba - Group number sequence inside a string
which the difference is that my item no. is in horizontal like below:
ColA(ID) ColB ColC ColD ColE ColF ColG
A 101 102 103
B 201 202 203 501 502
Sometimes for an ID, there will only have 3 item no., sometimes with 5, they can be upto 30 sometimes...
What I think the function could look like this: Cell G1 = lookupsequence(A1:A30), since that lookup function is no need in this situtation
Then G1 -> 101-103
Then G2 -> 201-203, 501-502
Below is the code I have based on that post, but just generating G1: 101, 102, 103
Lookupsequence(Return_val_col As Range)
Dim i As Long
Dim result As String
Dim initial As String
Dim separator As String
Dim preValue As Integer
Dim value As Integer
preValue = -1
separator = ""
For i = 1 To 30
value = CInt(Return_val_col.Cells(1, i).value)
If value - 1 = preValue Then
result = initial & "-" & value
Else
result = result & separator & value
initial = result
separator = ","
End If
Next
Lookupsequence = Trim(result)
End Function
I tried to add something like but not succeed
Dim lastcol As Long
lastcol = Cells(1, Columns.Count).End(xlToLeft).Column
For i = 1 To lastcol
Thank you

Answer 1

Assuming a max of 30 numbers within the limits of rownumbers of Excel, try:
Function GetSequence(rng1 As Range) As String
Dim rng2 As Range
For Each cl In rng1.SpecialCells(2, 1)
If rng2 Is Nothing Then
Set rng2 = Cells(cl.Value, 1)
Else
Set rng2 = Union(rng2, Cells(cl.Value, 1))
End If
Next
GetSequence = Replace(Replace(rng2.Address(False, False), "A", ""), ":", "-")
End Function
Invoke through: =GetSequence(B1:D1) or whichever range holding the numbers.
If numbers get too large and too many for the above function, try:
Function GetSequence(rng As Range) As String
Dim arr As Variant: arr = rng.Value
With CreateObject("System.Collections.ArrayList")
For Each el In arr
If IsNumeric(el) And el <> "" Then .Add el
Next
.Sort
For i = .Count - 1 To 0 Step -1
If i = .Count - 1 Then
GetSequence = .Item(i) & "|"
Else
If Val(GetSequence) = .Item(i) + 1 Then
If Mid(GetSequence, Len(.Item(i)) + 1, 1) = "-" Then
GetSequence = .Item(i) & Mid(GetSequence, Len(CStr(Val(GetSequence))) + 1)
Else
GetSequence = .Item(i) & "-" & GetSequence
End If
Else
GetSequence = .Item(i) & "," & GetSequence
End If
End If
Next
End With
GetSequence = Replace(GetSequence, "|", "")
End Function
It's abit verbose but this way can even insert empty or unsorted arrays of numbers:

Answer 2

I tested this code and it worked correctly for me. I returned to the page and saw the solution from JvdV; so I thought I'd post my solution too.
Option Explicit
Private Sub Test()
Dim result$
Dim WS As Worksheet
Set WS = ThisWorkbook.Sheets("Sheet3")
result$ = Lookupsequence(WS.Range("B1:AE1"))
result$ = Lookupsequence(WS.Range("B2:AE2"))
result$ = Lookupsequence(WS.Range("B3:AE3"))
End Sub
Private Function Lookupsequence(Return_val_col As Range) As String
Dim preValue%, value%
Dim i&
Dim result$, separator$
preValue = -1
result = ""
separator = ", "
For i = 1 To Return_val_col.count
value = CInt(Return_val_col.Cells(1, i).value)
If value = 0 Then
Exit For
ElseIf result = "" Then
result = value
ElseIf value - 1 <> preValue Then
result = result & "-" & preValue & separator & value
End If
preValue = value
Next
If value = 0 Then
value = preValue
End If
result = result & "-" & value
Lookupsequence = Trim(result)
End Function
My test data in two images from columns A to AE to test the possibility of 30 item numbers