Hi aeohagman,
The Excel and ASCII importing with STP files should dynamically adjust to the number of values in a given channel, but it does not, unfortunately, adjust dynamically to a larger number of channels than what is declared in the STP file. So the operative question for you is whether you are loading the Excel data "transposed", that is, loading a single row into a new DIAdem channel. If so, then additional rows will constitute additional channels, and you will not be able to import more than the original channel number declared in the STP file. Note that you CAN import fewer channels than are declared in the STP file.
But if you are loading Excel columns into DIAdem channels, which is true 90% of the time, then you should not be running into a row limitation.
Feel free to post your Excel file and the STP file, and we'll take a look at it,
Brad Turpin
DIAdem Product Support Engineer
National Instruments