Editing files in mime-repository (css) with abap

Hello,

I want to edit several css-files with an ABAP-programm, which are saved in the mime-repository. I want to use it, to do some changes on my stylesheets which I cant archive with the eclipse theme editor plugin. So I have do edit all selfmade css-changes, each time I generate the stylesheets with the themeEditor.

Because of this, i want a programm which do this changes for me ....

How can I open a .css-File, search for a string in this file and replace it with another string?

For example:

.....a}.urFontStd{font-size:small;font-style:normal;font-weight:normal}.urGrpBdyBox{background-color:#D7DBD2;border-color:#B5BBAD;border-style:solid;border-width:1px}.urGrpBdyBoxBgColor{background-color:#D7DBD2}.urGrpBdyBoxNoBorder{background-color:#D7DBD2}.urGrpBdyBoxPd.urGrpBdyBoxBgColorPd.urGrpBdyBoxNoBorderPd"

and replace it with

.urGrpBdyBox{background-color:#FFFFFF;border-color:#000000;border-style:solid;border-width:1px}

It should be possible, to replace strings with a different length....(in two ways...) ....

I'm new in ABAP, so I hope that somebody can help me