在VB中求一个字符串

A = "BEIJINGCHINA"
b = Mid(A, InStr(A, "j") + 4)
Print b

把"j"改成"J"，得到CHINA

谁知道你期望的是啥?

InStr(A, "j") =0
b=mid(A,4)= JINGCHINA 完全正确

instr(从第几个开始,字符串,查找的字符)
Mid(字符串, 开始字符, 字符个数)

A = "BEIJINGCHINA"
b = Mid(A, InStr(1, A, "J"), 4)
Print b
End Sub

返回JING

你的程序写错了:

把b = Mid(A, InStr(1, A, "J"), 4) 改为 b = Mid(A, InStr(1, A, J), 4) 就行了!!

你要做的是字符截取吧:
private sub command1_click()
dim j as string
dim A as string
dim b as string
j=inputbox("输入你要查找的字符:")
A = "BEIJINGCHINA"
b = Mid(A, InStr(A, j) + 4)
Print b
end sub