Pause Callback function to update GUI

Hi,

I'm reading in 4 serial strings to matlab, checking the data, and loading it to a GUI for display. My problem is I can't update the text boxes handles in my GUI because the callback function that reads the serial port is constantly running.

How can I pause serial reading execution in order to update my GUI?

Thanks in advance, sorry if this is too vague please let me know if you require any other information

Fiona