Want to change the dates in selected cells manually using a MACRO

Dear Forum,

I am working on a database which has been used and mis-used by several ex-employees each one adding his own date format which has a resulted in a big issue now...

There are three dates and which have different formats like "mm/dd/yyyy" also "dd/mm/yyyy" and some other formats too..

I tried changing the dates using formulas but in vain...since this date is a vital aspect of this databases tampering with it is too risky...

So , i have to manually change each date after checking and confirming it with another inter portal..

On most occassions the dates are mentioned as "dd/mm/yyyy" which need to be changed manually by changing the position of the first 2 characters to move in between and the 4,5th character of the dates to replace the 1,2 character and this has to be done over more than 5000 rows and 2 columns...

The second column also has the same date except that the logic in this second column is that this is a date which three years - 1 day away from the first date.

Ex: 1st date is mentioned incorrectly as - 07/06/2013 which is actually 6-Jun-13...and the second date will be 5-Jun-16.. ( Y+3, D - 1) where Y- Years & D is Days.

Well the reason of doing manually is to avoid any errors in case of any other format than specified..

So, I want someone to help me with a macro which can work on a selected range of data for two columns..

The end format I want is make the dates read "6-Jun-13" which any layman can understand..

Regards
e4excel

Thats the reason i have to do it manually as there is one date which suggests that these dates can be greater than this particular date which is the Exam Date which is given in the format - d-mmm-yy so the other two dates are the certificate dates and certificate expiry date..the certificate date is always either 1 or more days after the Exam Date...as the Exam can be on a working day and then if there are Holidays falling after that then it would delay the certificate generation date...

So this has to be done manually and so I am looking out for a Macro which can get this done slightly faster as well as with manual intervention....

I want the Macro to work on a selected range of cells, so that i can select two colums with a matris size of 2Col X more than 1 Row...

Regards
e4excel

I wish I had a chance to undo the bad...but the only way I can do it now is by manually changing the dates...

please find my sheet with the dates as explained ....I have scrapped the sensitive information...