VBA insert data next row if exists - excel

Question

(VBA Beginner) Row 15 is my first row of the table.
I can add data using a UserForm into Row 15 but i want to if i have data in Row 15 add into the next row (in my case Row 16 always +1) this is the function that im using:
Public Function GetLastRow(TargetWorksheet As Worksheet, ColumnNo As Variant) As Long
If TargetWorksheet Is Nothing Then Exit Function
GetLastRow = TargetWorksheet.Cells(TargetWorksheet.Rows.Count, ColumnNo).End(xlUp).Row
End Function
And this is my add button:
Private Sub CommandButton1_Click()
Dim sh As Worksheet
Set sh = ThisWorkbook.Sheets("OIL_")
Dim GetLastRow As Long
'Validações-----------------------------------------------------
If Me.txtID.Value = "" Then
MsgBox "Insira um ID!", vbCritical
Exit Sub
End If
If Me.txtDesc.Value = "" Then
MsgBox "Insira uma Descrição!", vbCritical
Exit Sub
End If
'---------------------------------------------------------------
If GetLastRow + 1 <= 15 Then GetLastRow = 15 Else GetLastRow = GetLastRow + 1
sh.Cells(GetLastRow, 2).Value = Me.txtID.Value
sh.Cells(GetLastRow, 11).Value = Me.txtDesc.Value
sh.Cells(GetLastRow, 29).Value = Me.txtData.Value
End Sub
For now its only inserting data into my Row 15 and if i try to add another one it just replaces for the new data, i tried a lot of things and i cant manage to add data into the next row always.

Answer 1

Your function is named the same as your variable, this is confusing and if you debug your code you will find the GetLastRow will always equal zero and that is causing your issue. My biggest suggestion is to learn to use the debugger!
You could change your code to something like this:
Private Sub CommandButton1_Click()
Dim sh As Worksheet
Set sh = ThisWorkbook.Sheets("OIL_")
Dim lastRow As Long
'Validações-----------------------------------------------------
If Me.txtID.Value = "" Then
MsgBox "Insira um ID!", vbCritical
Exit Sub
End If
If Me.txtDesc.Value = "" Then
MsgBox "Insira uma Descrição!", vbCritical
Exit Sub
End If
'---------------------------------------------------------------
lastRow = GetLastRow(sh, 3) 'I am not sure what column you need I just used 3 for example
If lastRow + 1 <= 15 Then lastRow = 15 Else lastRow = lastRow + 1
sh.Cells(lastRow, 2).Value = Me.txtID.Value
sh.Cells(lastRow, 11).Value = Me.txtDesc.Value
sh.Cells(lastRow, 29).Value = Me.txtData.Value
End Sub

Answer 2

Well, problem solved this is the right way to do it
Private Sub AddButton_Click()
Dim sh As Worksheet
Set sh = ThisWorkbook.Sheets("OIL_")
Dim lastRow As Long
'Validações-----------------------------------------------------
If Me.txtID.Value = "" Then
MsgBox "Insira um ID!", vbCritical
Exit Sub
End If
If Me.txtDesc.Value = "" Then
MsgBox "Insira uma Descrição!", vbCritical
Exit Sub
End If
'---------------------------------------------------------------
lastRow = GetLastRow(sh, 2)
If lastRow + 1 <= 15 Then lastRow = 15 Else lastRow = lastRow + 1
sh.Cells(lastRow, 2).Value = Me.txtID.Value
sh.Cells(lastRow, 11).Value = Me.txtDesc.Value
sh.Cells(lastRow, 29).Value = Me.txtData.Value
End Sub
And this is the right function:
Public Function GetLastRow(TargetWorksheet As Worksheet, ColumnNo As Variant) As Long
If TargetWorksheet Is Nothing Then Exit Function
GetLastRow = TargetWorksheet.Cells(TargetWorksheet.Rows.Count, ColumnNo).End(xlUp).Row
End Function
Thanks to everyone