SQL & PL/SQL :: DECODE And CASE In WHERE Clause

I am facing a problem while retrieving data from table using DECODE/CASE.

Table: PARAM_MSTR

MIN_VALMAX_VALPARAM_CODE DESCRIPTION DATATYPE
AB1000 HARD PARAMETERTEXT
CN1000 SOFT PARAMETERTEXT
0501001 CRYSTAL PARAMETERNUMBER
512001001 STONE PARAMETERNUMBER

Now I want to get the parameter description based upon the PARAM_CODE and a value passed which should be in range of MIN_VAL and MAX_VAL. Means when I pass PARAM_CODE=1000 and :parameter=A, then it should check the DATATYPE of the PARAM_CODE, in our case it is 'TEXT' so it should check the passed value between MIN_VAL and MAX_VAL like

:parameter BETWEEN MIN_VAL AND MAX_VAL and should return 'HARD PARAMETER'.
If I pass PARAM_CODE=1001, then the DATA_TYPE is 'NUMBER', so it will check the :parameter value as Number.
Like :parameter BETWEEN to_number(MIN_VAL) AND to_number(MAX_VAL)

For example:
PARAM_CODE :parametr Result
1000 A HARD PARAMETER
1000 C SOFT PARAMETER
1000 P NULL
1001 25 CRYSTAL PARAMETER
1001 99 STONE PARAMETER
1001 201 NULL

I have written a query using DECODE and CASE statement but it is not working properly.

SELECT * FROM param_mstr WHERE PARAM_CODE=1000 AND :parameter BETWEEN DECODE(DATATYPE,'NUMBER',CAST(MIN_VAL as NUMBER),MIN_VAL)AND DECODE(DATATYPE,'NUMBER',CAST(MAX_VAL as NUMBER),MAX_VAL)