How to remove data from string builder

Hi i all having a requirement to delete particular data from a text file. I have written some code to get my exact data to remove but now i am little bit confused in removing that particular data can any one help me.

Initially this is my data in text file where i am storing to a Stringbuilder

101 111111111 1111111111110150105A094101                                                      

52201               1                   1         PPD1         111015111015   1111000020000001

6241110000251                00000000011              1                     1 0111000020000001

822000000100111000020000000000000000000000011                                  111000020000001

52251               1                   1         PPD1         011015111015   1111000020000002

6281110000251                00000000011              1                     1 0111000020000002

822500000100111000020000000000010000000000001                                  111000020000002

9000002000001000000020022200004000000000001000000000001                                       

Now by using certain code i am getting the data to delete i.e assume i would like to delete from 5 to 8 which exists. I am storing this to another StringBuilder as follows

52251               1                   1         PPD1         011015111015   1111000020000002

6281110000251                00000000011              1                     1 0111000020000002

822500000100111000020000000000010000000000001                                  111000020000002

I would like to remove this from the main Stringbuilder i am having. Is this the correct process or if any better way let me know

Tags: C# 3.5, String