Search for value in a range and overwrite if found and create new if not found

what does this mean.

If found, overwrite (or do nothing)

try this:

Option Explicit

Sub datefind()
    Dim lr As Long
    Dim i As Long
    lr = Range("A" & Rows.Count).End(xlUp).Row
    Application.ScreenUpdating = False
    For i = 1 To lr
        If Range("A" & i) = Range("B2") Then
            Exit Sub
        Else: Range("A" & lr + 1) = Range("B2")
        End If
    Next i
    Application.ScreenUpdating = True
    MsgBox "Complete"
End Sub

If that takes care of your original question, please select Thread Tools from the menu link above and mark this thread as SOLVED. Thanks for the rep

Suggest you post (upload) a sample worksheet for testing. I ran on a sample I made and it worked as requested.

The reason it does not work, is you have placed the value to compare in cell B1. Your post #1 indicated that this value is in B2. If you place the date in B2, it will work. If you want to compare it to B1, change the code to read B1 instead of B2.

Yup! You are right. Will work on this today.

Here is a new solution:

Option Explicit

Sub datefind()
    Dim lr As Long
    Dim i As Long
    lr = Range("A" & Rows.Count).End(xlUp).Row
    Application.ScreenUpdating = False
    Dim res As Variant
    On Error Resume Next
    res = Application.WorksheetFunction.Index(Range("A1" & ":A" & lr), Application.WorksheetFunction.Match(Range("B2"), Range("A1" & ":A" & lr), 0))
    If Err = 0 Then
        Exit Sub
    Else: Range("A" & lr + 1) = Range("B2")
    End If
    Application.ScreenUpdating = True
    MsgBox "Complete"
End Sub