VBA debug issue - excel

Question

This macro runs on the click of a button. I receive an error.
Run-time error '91':
Object variable or With block variable not set
I click Debug and it leads me to this highlighted area.
Selection.Find(What:=DateString, After:=ActiveCell, LookIn:=xlFormulas, _
LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
MatchCase:=False).Activate
Here is the entire function
Function GetBalance(Month As Integer) As Currency
'This function is called by the Calculate_Balance subroutine. It
'finds the appropriate month's balance on an employee sheet and sends
'it back to the calling routine.
Dim DateString As String
Dim RangeString As String
Dim Balance
Dim BalDate As Date
Dim strCurrMonth As String
Dim strCurrYear As String
Dim strFirstDayCurrMonth As String
strCurrMonth = CStr(DatePart("m", Date))
strCurrYear = CStr(DatePart("yyyy", Date))
strFirstDayCurrMonth = strCurrMonth & "/1/" & strCurrYear
dtmFirstDayCurrMonth = CDate(strFirstDayCurrMonth)
DateString = Month & "/1/"
Columns("A:A").Select
Range("A6").Activate
Selection.Find(What:=DateString, After:=ActiveCell, LookIn:=xlFormulas, _
LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
MatchCase:=False).Activate
CurrRow = ActiveCell.Row
BalanceRow = CurrRow - 1 'Move up 1 row to get last balance for this month
RangeStr = "E" & BalanceRow
DateRangeStr = "A" & BalanceRow
BalDate = Range(DateRangeStr).Value
If BalDate <= dtmFirstDayCurrMonth Then
Balance = Range(RangeStr).Value
Else
Balance = 0
End If
GetBalance = Balance
End Function

Answer 1

The Find() function returns a Range object so with your code if nothing is found, you will get a error as it can not 'activate' nothing. Change the code to something like:
Dim rng As Range
Set rng = Selection.Find(What:=DateString, After:=ActiveCell, LookIn:=xlFormulas, SearchDirection:=xlNext, MatchCase:=False)
If Not (rng Is Nothing) Then
rng.Activate
End If