Unless there's a piece of data somewhere in the file that contains the number of lines so you can set the repeat count in textscan programmatically, you can't do anything specific to the count a priori.
Probably there's a regexp pattern that could be written to find the terminator but I'm not expert enough to work it out w/o a fair amount of effort so won't give a go.
Otherwise, either
a) continue to read/parse the file line-by-line looking for the termination string, or
b) read the whole file into memory as array of cell strings then locate the sections by string comparison operations and operate on those in memory.
