По поводу замены символа смотри Replace.
А по поводу сроки ввода смотри переменную mat.

авторDescription

Returns a string in which a specified substring has been replaced with another substring a specified number of times.

Syntax

Replace(expression, find, replace[, start[, count[, compare]]])

The Replace function syntax has these named arguments:

Part Description
expression Required. String expression containing substring to replace.
find Required. Substring being searched for.
replace Required. Replacement substring.
start Optional. Position within expression where substring search is to begin. If omitted, 1 is assumed.
count Optional. Number of substring substitutions to perform. If omitted, the default value is –1, which means make all possible substitutions.
compare Optional. Numeric value indicating the kind of comparison to use when evaluating substrings. See Settings section for values.
Одна проблема. По-моему, она не поддерживается в 97 экселе.

Дмит k-nike ответил сразу, недожевал однако :)
Был бы talgat девушкой дожевал бы...)))