If you are still programming on Amstrad CPC, you are maybe using WinAPE. But its assembler has limitations. For example, if you want to create a .DSK, a .SNA, compile something, compact something BEFORE or AFTER assembling, it's not possible in 1 pass and 1 key press. But it's now possible with some additional software (freeware).

For more informations go to Grimaware, and for the direct link in (english, check end of page for the update) about the Amstrad CPC cross-development kit, it's there.