Your First Workplace Macro | Decoding VBA

Goal

Combine variables, loops, and conditionals into one macro you could run before sending a report.

When to use this

Run this pattern when a recurring export needs a quick validation pass: blank checks, sign checks, or required field checks.

Worked example

Imagine a Report sheet with amounts in column C and owners in column B. You want column D to flag rows that fail basic rules.

Option Explicit

Sub ValidateReportTab()
    On Error GoTo ErrorHandler

    Dim ws As Worksheet
    Dim lastRow As Long
    Dim rowIndex As Long
    Dim issueCount As Long

    Application.ScreenUpdating = False
    Set ws = ThisWorkbook.Worksheets("Report")
    lastRow = ws.Cells(ws.Rows.Count, "A").End(xlUp).Row

    For rowIndex = 2 To lastRow
        ws.Cells(rowIndex, "D").ClearContents

        If Len(ws.Cells(rowIndex, "B").Value) = 0 Then
            ws.Cells(rowIndex, "D").Value = "Missing owner"
            issueCount = issueCount + 1
        ElseIf Not IsNumeric(ws.Cells(rowIndex, "C").Value) Then
            ws.Cells(rowIndex, "D").Value = "Invalid amount"
            issueCount = issueCount + 1
        ElseIf ws.Cells(rowIndex, "C").Value < 0 Then
            ws.Cells(rowIndex, "D").Value = "Negative amount"
            issueCount = issueCount + 1
        Else
            ws.Cells(rowIndex, "D").Value = "OK"
        End If
    Next rowIndex

    Application.ScreenUpdating = True
    MsgBox "Validation complete. Issues found: " & issueCount, vbInformation, "Decoding VBA"
    Exit Sub

ErrorHandler:
    Application.ScreenUpdating = True
    MsgBox "Error " & Err.Number & ": " & Err.Description, vbCritical, "Decoding VBA"
End Sub

What to notice

• Option Explicit and typed variables (Long, Worksheet).
• No Select or Activate—the code talks directly to ws.
• ScreenUpdating = False during the loop for speed on large tabs.
• On Error GoTo so a bad sheet name does not leave Excel in a half-updated state.

Common mistakes

• Validating the active sheet instead of a named tab (breaks when someone clicks elsewhere).
• Writing “OK” only on the last row because the loop variable was wrong.
• Forgetting to re-enable ScreenUpdating in the error path.

Practice

Add a rule: if column C is greater than 1,000,000, flag "Review threshold". Then run the macro on a copy of a real workbook.

Next up

Move to the Intermediate track and load data into arrays for faster processing.

Back to Beginner lessons