Generation of sequential serial number based on prefix value - excel

Question

We have prefix defined already (say ABC, GIJ, THK, JLK ...so on) and want to create a sequential number when a user wants to generate a number for each of these prefix like given below:
ABC0000 , ABC0001 , ABC0002 ...ABC9999 same for GIJ0000 , GIJ0001 , GIJ0002 ...GIJ9999.
Given below is the code written for the above logic, but it does not achieve the requirement:
Private Sub CommandButton1_Click()
With ComboBox1.Value
Dim a, b As String
Dim i, j, k, l, x, q, m, temp As Long
a = ComboBox1.Text
i = Application.WorksheetFunction.Match(a, Range("A1:A1000"), 0)
j = Cells(i, 2)
l = j * 1000
For q = 2 To 100
For m = 2 To 100
If Cells(q, m).Value < 0 Then
k = m
End If
Next
Next
x = l
If Cells(i, GC).Value = temp Then
click = click + 1
Else
click = 0
End If*
Cells(i, GC) = x + click
TextBox1.Text = x + click
temp = Cells(i, GC).Value
End With
GC = GC + 1
End Sub

Answer 1

VBA does not seem necessary for this. Assuming you have your prefixes in separate cells in ColumnA starting in Row1, put in B1:
=A1&TEXT(COUNTIF(A$1:A1,A1)-1,"0000")
and double-click its fill handle.

Answer 2

From your code, I assume that you have a ComboBox named ComboBox1, a CommandButton named CommandButton1 and a TextBox named TextBox1, all on a UserForm, and with ComboBox1 filled with the possible values for prefixes.
The following code will put the next available code(1) for the selected prefix into the TextBox.
Private Sub CommandButton1_Click()
Dim a As String
Dim i As Long, j As Long
a = ComboBox1.Text
i = Application.WorksheetFunction.Match(a & "9999", Range("A1:A1000"), 1)
j = CLng(Mid$(Cells(i, 1).Value, Len(a) + 1)) + 1
TextBox1.Text = a & Format(j, "0000")
End Sub
Your code is also doing a lot of unnecessary stuff.
(1) only if data is sorted.