internal tables

I am having a flat file which contains a field named matnr.

i nedd to declare a internal table with field matnr1 and matnr 2.

my problem is in my flat file they may be 10 material numbers or 100.

so looking how to declare an internal table dynamically so that my internal table should contain 10 material matnr1....matnr10 if it contains 100 internal table should contain matnr1..............matnr100.

if not able to understand please do reply