Find Starting Date And Fill In The Following Months Until End Date

I have collected some data on economic factors for different countries. Unfortunately, the dates when I started to calculated my economic factors are different for each country (due to the data available to me).

What I would like Excel to have done is to take the date when I started to measure for e.g. country A (D3 ie 30/06/2007), copy it into column "I" (for country A, it's cell I3) and fill in the following months in the rows below (with always the date of the last day of a month) until it reaches 28th of Feb 2013. Then, it should go up to the next country (country B) take the starting date (D4, ie 31/07/2007), go to the last entry in "I" (ie I71) and paste the date in, fill in the months until 28th of Feb 2013, do the same for country C and so on.

I have started to code a VBA but I am unfortunately a beginner in VBA and totally stuck at the moment. My VBA code does paste in the months but for some reason, it also changes the starting date of the first month.

Moreover, I tried a workaround for the fact that Excel doesnt know when to stop; ie I introduced a "monthdiff" variable which should calculate the number of months between the starting date (which is variable and unique for each country) and the end date (which is always 28th of Feb 2013). At the moment, it only does this for country A.

VB:
Set rng = ActiveSheet.Range("I3" & Cells(monthdiff, "I").Address)[SIZE=4][/SIZE]

I have tried to make this dynamic but have been unsuccessful so far.

Spreadsheet with data&code is attached.

VB:
Sub Macro1()
Dim mainrange As Range
Dim rng As Range

[Code].....