Fill In Date And Time Where Missing On 3 Minutes Interval

I am having trouble getting a VBA code to do the following:

2012/05/01 00:00:00
2012/05/01 00:03:00
2012/05/01 00:06:00
2012/05/01 00:15:00
2012/05/01 00:18:00

From this above to this below

2012/05/01 00:00:00
2012/05/01 00:03:00
2012/05/01 00:06:00
2012/05/01 00:09:00
2012/05/01 00:12:00
2012/05/01 00:15:00
2012/05/01 00:18:00

There are data entries next to these time stamps. I am able to create just the time stamps starting at the beginning and ending at the end of the month but I need it to fill in missing entries in a data set. The code below works but only some of the time. I have tried a few different things but nothing works.

Code:
Sub Insert_missing_3min()
'Inserts a row with the date and time where the missing date and time stamp is and a zero next to the date added.

Dim min3 As Date
Dim CurTime As Date
Dim CurCell As Date
Dim NextCell As Date

min3 = 3 / 24 / 60

[Code] ........