The function CHRW(UnicodeValue) in VBA returns Unicode character;
The function UNICODE(TextString) in VBA returns Unicode value of 1st character in TextString.

You can use REPLACE() in VBA to replace one Unicode/ASCII character in call with another one;
Or you can give an ReplaceAll command to replace one Unicode/ASCII character on worksheet with another one.

So general approach for VBA procedure will be:
Create 2-dimensional array with Unicodes for characters to be replaced and to replace to;
a) Cycle through all cells in used area in worksheet. For every cell cycle through array to replace the character;
b) Cycle through array. For every character to be replaced invoke ReplaceAll for worksheet.