Thanks to Martin McClure I could create some FFI classes.
But there's a item I still don't understand
Whe you have a DLL function that returns not only the function value but a 
var parameter indeed, how can I access it from Squeak?
This is the case:

apiIsisRecField: aHandle at: index tag: aTag occ: nOcc field: cField long: 
lField
	<apicall: long 'IsisRecField' (long long long long char* long) module: 
'isis32.dll'>
      ^self externalCallFailed

In Delphi, for example, I can call this function that way:

Var s:PChar;
r,handle,tag,nOcc,lField: LongInt;
//give some values to the variables and allocate PChar (Uff!!!!)
r:= IsisRecField(handle,tag,nocc,s,lfield);

// and s is the value I really need, r is not very important, but the FFI 
class give this value