Eliminate a part of a string

Hello there,
I would like to eliminate a part of a string starting from a position recorded in another variable for 2000 characters backward. I can't use dataex as the strings are very long.

To give you an example let's say I want to eliminate the word BB (hence appearing at position 6) from the string text and the 3 characters before

text: AAAA BBC D
Bpos: 6
Wanted: AAC D

Thank you,

Ylenia