Convert String Into Test?

I am building an application to update a database.I have a Map table where row 0 holds the target table field name Row 1 holds an update value or Source table Column name Row 2 holds a Where condition eg

Map: CustNo CustName Val1 Val2
Update: 25
Where: =[CustNo] > [Fld14]

In this example I am going to update the Target Table Field 'Val1' to 25 where the Target Table Rows have Field 'Val1' data > 14 AND Target Table Field 'CustNo' = the Source Table Field 'CustNo' AND the Target Table Field 'Val1' > the Source Table Field 'Fld14' Where I am stuck is I at the moment is wondering how I should convert the strings into test conditions as I iterate the Target Table eg Say my test string is stTest and it holds " = 25" For each dr as datarow in dtTarget

some code

... stFld = "Val1"
if dr(stFld) { convert stTest into literal '=' and then 25}

... do something the only way I can think is to build up a series of test cases like:

Select stOp
Case stOp = "="
Case stOp = "<>"
etc.