MidB Statement

Replaces a specified number of bytes in a Variant (String) variable with bytes from another string.

Syntax

MidB(stringvar, start[, length]) = string

• stringvar: Required. Name of string variable to modify
• start: Required. Byte position where replacement begins (1-based)
• length: Optional. Number of bytes to replace. If omitted, uses entire length of string
• string: Required. String expression used as replacement

Remarks

• MidB is used with byte data contained in a string
• Works with byte positions rather than character positions (important for double-byte character sets)
• The number of bytes replaced is always less than or equal to the number of bytes in stringvar
• If start is greater than the number of bytes in stringvar, stringvar is unchanged
• If length is omitted, all bytes from start to the end of the string are replaced
• MidB statement replaces bytes in-place; it does not change the byte length of the original string
• If replacement string is longer than length, only length bytes are used
• If replacement string is shorter than length, only available bytes are replaced
• Primarily used when working with double-byte character sets (DBCS) like Japanese, Chinese, or Korean

Examples

Dim s As String
s = "ABCDEFGH"
MidB(s, 3, 2) = "12"       ' Replaces 2 bytes starting at byte 3

' For DBCS strings:
Dim dbcsStr As String
dbcsStr = "日本語"          ' Japanese characters
MidB(dbcsStr, 1, 2) = "XX" ' Replaces first 2 bytes

Reference

MidB Statement - Microsoft Docs