Expand Start Date to End Date with Series of EOMONTHs

Question

I have a data table containing ids with a start date and end date associated with both.

RowNo   AcNo     StartDate     EndDate
  1     R125     01/10/2017            


        

Answer 1

Try it as a nested For ... Next loop using DateDiff to determine the number of months. Collecting the progressive values in an array will speed up execution before dumping them back to the worksheet.

Option Explicit

Sub eoms()
    Dim a As Long, m As Long, ms As Long, vals As Variant
    With Worksheets("Sheet2")
        .Range("F1:G1") = Array("AcNo", "EOMONTHs")
        For a = 2 To .Cells(.Rows.Count, "B").End(xlUp).Row
            ms = DateDiff("m", .Cells(a, "C").Value2, .Cells(a, "D").Value2)
            ReDim vals(1 To ms + 1, 1 To 2)
            For m = 1 To ms + 1
                vals(m, 1) = .Cells(a, "B").Value2
                vals(m, 2) = DateSerial(Year(.Cells(a, "C").Value2), _
                                        Month(.Cells(a, "C").Value2) + m, _
                                        0)
            Next m
            .Cells(.Rows.Count, "F").End(xlUp).Offset(1, 0).Resize(UBound(vals, 1), UBound(vals, 2)) = vals
        Next a
        .Range(.Cells(2, "G"), .Cells(.Rows.Count, "G").End(xlUp)).NumberFormat = "mmm yy"
    End With
End Sub

VBA's DateSerial can be used as a EOMONTH generator by setting the day to zero of the following month.

Note in the following image that the generated months are the EOMONTH of each month in the series with mmm yy cell number formatting.