Hi shankle,
Here is a quick example for you :
#define uppercase testlib.lib:uppercase
#define lowercase testlib.lib:lowercase
#define StdOut testlib.lib:StdOut
.data
str1 db 'string converted to uppercase.',13,10,0
str2 db 'THIS STRING CONVERTED TO LOWERCASE.',0
.code
start:
invoke uppercase,ADDR str1
invoke StdOut,eax
invoke lowercase,ADDR str2
invoke StdOut,eax
invoke ExitProcess,0