Regnar,
Sure no problem. You might want to read the following document from Xylotex if you haven't already
http://www.xylotex.com/XS3525V400.pdf. Page 6 has the enable info. Basically there is a 5 pin header between the parallel port and the breakout screw terminals. You remove the jumper from the enable pins located by the step setting jumpers. This will take it out of enable mode. Then connecting a switch between the ground on the 5 pin header and the other 4 pins. Closing the switch will then enable the drive. I have a DeskCNC board so I use it for my E-Stop which requires a normally closed switch.
Header Connections
Using 1 Switch ($) to enable/disable all drivers at once.
X Y Z A Ground
| | | | ` $
| | | |___|
| | |_____|
| |_______|
|_________|
Using 4 Switches ($) to enable/disable individual drivers.
X Y Z A Ground
| | | | ` |
| | | $___|
| | $_____|
| $_______|
$_________|