macro combining find and sendkeys

Hi,
is there a way to create a macro that makes it possible to use a find-function and a sendkeys-function (shell.SendKeys( "{BACKSPACE}" )) in one text-file?
I want to combine pairs of two lines of text to one line. The second line of the pairs always starts with the same character (here ":") and should be placed after the first line of the pairs.
Sample:

AAA
:BBB

CCC
:DDD

EEE
:FFF

Here follows how I want to have the text after using a macro:

AAA:BBB

CCC:DDD

EEE:FFF

Can anyone give me the syntax of the macro, please?

Thanks a lot in advance...

No need for macros.
Press CTRL + H
find: "n(:.*)"
replace with : "1"
check use regular expressions
replace all
Done

Thanks a lot... :-)