vba access getting exceeded system resources error - vba

Question

Running the code below on access 2013 I get a system resource error. My understanding is that the program can take more time but the system resource error does not make sense. My laptop has 8gb RAM and core i3. Is there a better way to do this? Values used:
me.yearsback= 1
me.valdate = 5/31/2016
me.period = "monthly"
UPDATE: Used 0.5M rows first, producing the system resource error. However, when I reduce the number of rows, it runs fine.
:
Option Compare Database
Private Sub Calculate_Click()
Dim db As Database
Dim rs As Recordset
Dim x As Integer
Dim y As Integer
Dim Months As Integer
Dim WPmonthly As String ' field name for monthly written premium
Dim UPRmonthly As String ' field name for monthly unearned premium
Dim EPmonthly As String ' field name for monthly earned premium
Dim runningDate As Date
Dim runningDate2 As Date
Dim useDateLower As Date
Dim useDateUpper As Date
Months = Me.YearsBack * 12 + Month(Me.ValDate)
If Me.Period = "monthly" Then
Set db = CurrentDb
For x = 1 To Months
runningDate = Format(DateAdd("m", -x + 1, Me.ValDate), "mm yyyy")
WPmonthly = "WP M" & Month(runningDate) & " " & Year(runningDate)
EPmonthly = "EP M" & Month(runningDate) & " " & Year(runningDate)
UPRmonthly = "UPR M" & Month(runningDate) & " " & Year(runningDate)
db.Execute "ALTER TABLE tblEPdata ADD COLUMN [" & WPmonthly & "] STRING;"
db.Execute "ALTER TABLE tblEPdata ADD COLUMN [" & EPmonthly & "] STRING;"
db.Execute "ALTER TABLE tblEPdata ADD COLUMN [" & UPRmonthly & "] STRING;"
If x = Months Then
runningDate = Format(DateAdd("m", -x, Me.ValDate), "mm yyyy")
UPRmonthly = "UPR M" & Month(runningDate) & " " & Year(runningDate)
db.Execute "ALTER TABLE tblEPdata ADD COLUMN [" & UPRmonthly & "] STRING;"
End If
Next
For y = 1 To Months
runningDate2 = Format(DateAdd("m", -y + 1, Me.ValDate), "mm yyyy")
useDateLower = runningDate2
useDateUpper = Format(DateAdd("m", -y + 2, Me.ValDate), "mm yyyy")
WPmonthly = "WP M" & Month(runningDate2) & " " & Year(runningDate2)
EPmonthly = "EP M" & Month(runningDate2) & " " & Year(runningDate2)
UPRmonthly = "UPR M" & Month(runningDate2) & " " & Year(runningDate2)
Set rs = db.OpenRecordset("tblEPdata", dbOpenDynaset, dbSeeChanges)
Do Until rs.EOF
'Written Premium Calculation
If rs!issueDate < useDateUpper And rs!issueDate >= useDateLower Then
rs.Edit
rs.Fields(WPmonthly) = rs!grossPremium
rs.Update
End If
'UPR Calculation
If rs!issueDate < Me.ValDate Then
If rs!expiryDate < useDateUpper Then
rs.Edit
rs.Fields(UPRmonthly) = 0
rs.Update
ElseIf rs!effectiveDate < useDateUpper Then
rs.Edit
rs.Fields(UPRmonthly) = (rs!expiryDate - useDateUpper + 1) / (rs!expiryDate - rs!effectiveDate + 1) * rs!grossPremium
rs.Update
ElseIf rs!effectiveDate >= useDateUpper Then
rs.Edit
rs.Fields(UPRmonthly) = rs!grossPremium
rs.Update
Else:
rs.Edit
rs.Fields(UPRmonthly) = rs!grossPremium
rs.Update
End If
End If
rs.MoveNext
Loop
rs.Close
Next
End If
db.Close
End Sub