Finding Value in Last Cell and Comparing Data to Run Macro - excel

Question

*EDIT
Here is what ended up kind of working. The solutions below do not run the AddProj when new row is inserted.
Sub Worksheet_Calculate()
Dim X As Range
Set X = LastCell 'The X is superflous, you could just use the LastCell variable
If Sheet5.Range("A" & Rows.Count).Value < X.Value Then
X.Value = Me.Range("A" & Rows.Count).Value
AddProj
End If
End Sub
Module 1 contains the following:
Function LastCell() As Range
With Sheet5
Set LastCell = .Cells(Rows.Count, 1).End(xlUp)
End With
End Function
Sub AddProj()
Sheet1.Range("Master").Copy Sheet1.Range("C" & Rows.Count).End(xlUp).Offset(1)
End Sub
I am trying to read the data in the last cell of a column.
The value of "X" should be the value of this last cell.
I then want "X" to be compared to the number of rows and if the number of rows is less than "X", perform my macro "AddProj".
Once "X" and Column A are the same value, nothing else is to be done.
For some reason, it is not working.
This code is on the worksheet where I want the comparison to be made.
Please see my code below:
Private Sub Worksheet_Calculate()
X = LastCell
If Sheet5.Range("A" & Rows.Count).Value < Sheet5.Range("X").Value Then
Sheet5.Range("X").Value = Me.Range("A" & Rows.Count).Value
AddProj
End If
End Sub
Sub LastCell()
Range("A1").End(xlDown).Select
End Sub
The "AddProj" is a module that is referenced in the code above (thank you #jsheeran #SJR ACyril for help):
Sub AddProj()
Sheet1.Range("Master").Copy Sheet1.Range("C" & Rows.Count).End(xlUp).Offset(1)
End Sub
Thanks in advance.

Answer 1

Try this:
Sub Worksheet_Calculate()
Dim lRow As Long
lRow = Sheet5.Cells(Sheet5.Rows.Count, 1).End(xlUp).Row
If Sheet5.Cells(lRow, 1) > lRow Then
Sheet5.Cells(lRow, 1) = lRow
AddProj
End If
End Sub
X is a variable but you refer to it as "X". Also avoid using .Select as it is not necessary and even in this case just does nothing, because first of all a Sub cannot return a value and second .Select has also no return value. The best way to calculate the last row is this: Sheet5.Cells(Sheet5.Rows.Count, 1).End(xlUp).Row

Answer 2

Here is just a slight variation on UPGs great answer.
Dim lRow As Long
lRow = Sheet1.Cells(Sheet1.Rows.Count, 1).End(xlUp).Row
If lRow >= Sheet1.Cells(lRow, 1) Then
Exit Sub
Else: AddProj
End If