Which method to check these types of md5 inputs

[mastercracker]

Is there a particular best way to approach checking passwords where I have a large part of the md5 input, and the hash, but there is a section of 'random' variation?

Such as:

1234567890?????qwertyuiop


Where I know the prefix and suffix, but not the length of the ? section, not the values. I was trying to construct a dictionary with each ? of a single length, then a set of rules that would try a character set but I had little success so far.

Use masks. Check the wiki if you don't know how. You will have to create a mask for each length that you want to try.