I am not quiet sure which language you are using but this might help. It states that there is a parameter named: ungapped_alignment. This is probably a boolean value so you should set it to true.

If you are able to make a blast by hand: The blastall program has a parameter -g. For ungapped alignment you should set it to -g F

Here are two options that will work:

One option: Set -G and -E to high values. -G is the gap opening penalty and -E is the gap extension penalty.

Second option: Set -g to F, where -g is the binary switch to perform a gapped alignment.