First you will have to coerce the I32 into an I16 because an I32 would consist of 4 bytes. This will effectively limit your range from -2147483648 to +2147483647, to -32768 to +32767. But that probably won't be a problem. Look on Numeric palette, Conversion for that function.
Then look on Numeric palette, Data Manipulation for the split number function to take the I16 into 2 I8's. then you can coerce to 2 U8's.
You can probably do this more simply as coerce I32 to U16, then split to 2 U8's. But I'll leave that for you to experiment with.