seek trough files in vhdl

[Maki]

Hello all,

I'm trying to insert initialization strings for Block RAM in UCF file from a
testbench.
The only thing I manage to do is to append INITs to UCF file. I don't see
the solution to delete the previous INIT strings and then write a new one.
For
now I delete old strings manualy.
Basicaly I have to search through file and when i find some kind of control
string I have to overwrite with new content.
And this is all because Xilinx ISE don't support more then one UCF file.

Anybody have an idea of how to do this from vhdl?

Thanks for any input,

Best regards,
M.