Concatination of Two dates in customer exit Variable

HI Expert ,

I am writting customer Exit Variable to get Records from user entered Dates .

Eg. In Variable Screen of Bex report i have 2 Variable LYDate & TY Date both of them are As "Mutiple Single Value" & "Mendetory".

If we give LYDATE and TYDATE Date range as,

LYDate - 01/2013 - 06/2013

TYDate - 01/2014 - 12/2014

So I need ABAP Code which will get Value Range from 01/2013 from LYDATE and 12/2014 From TY DATE . So Query will Get data for 01/2013 TO 12/2014 (2 Years Data).

ZCALYEAR (Cusomer Exit)  = LYDATE (01/2013)  TO TY DATE(12/2104).

Please provide step by step ABAP Code to Achiev above issue. Points for Sure...

Thanks,

GB