Dosbox 0.72 Keyboard Mapper problem

[scribelog]

Hi I have installed Doom 2 no problems until I come to play it on my HP Laptop. I have attempted to change forward & back using keyboard mapper to the cursor movement keys and have no problems with left & right but forward & back wont map or work. I have edited C:\Valve\Steam\steamapps\common\Doom 2\base\default.cfg to 850 UK Keyboard layout, but still can't get it to work. I have a Micrrosoft mouse attached and I am wondering if that could be causing an issue Any ideas ? thanks