>Both Integer and Long cause a "Declare DLL call caused an exception".
>
>DECLARE Integer ASX_System_Create IN asX32.dll Integer, Integer @
>
>PRIVATE lReturn
>lReturn = ""
>
>PRIVATE lHandle
>lHandle = 0
>
lReturn = ASX_System_Create(1, @lHandle)

There's no difference between Integer and Long in DLL declaration.
The DECLARE and call looks correct to me but lets try this

DECLARE Integer ASX_System_Create IN asX32.dll Integer, String @
lcHandle = REPLICATE(CHR(0),8)
lReturn = ASX_System_Create(1, @lcHandle)