how to delete the whole string whose starting and ending text i have.

[herit02]

it was regarding in vb.net text operations, i want to replace the text by finding some particular text.

but the problem arises when the starting and the at the end delimiter of the string is something same every-time but middle thing keeps on changing so how can i work out with that??
eg:

str = Replace(str, "abcdparameter = xyz123;", "abcdarameter = my defined parameter;")

i tried to learn some regular expressions but i am not able to get that.
the xyz 123 is same every-time....and also there is one delimiter at the end of the parameter string so anyhow you can select the whole line and replace it.

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[Mariandi]

I know is not exactly what you want but u can use the split function to get the string after xyz123 and the again the same for the end delimiter and the
concatenate the start & middle & end as you like

[GeekByChoiCe]

Could you post some example lines?
I think you were on the right track with regular expressions.